C1-symmetric rare-earth-metal aminodiolate complexes for intra- and intermolecular asymmetric hydroamination of alkenes

Article abstract of DOI:10.1021/om3010614

A series of novel C₁-symmetric aminodiolate rare-earth-metal complexes have been prepared via arene elimination from [Ln(o-C ₆H₄CH₂NMe₂)₃] (Ln = Y, Lu) and the corresponding aminodiol proligand. The NOBIN-derived aminodiolate ligands feature sterically demanding triphenylsilyl and methyldiphenylsilyl ortho substituents on the naphtholate moiety and substituents of varying steric demand ranging from tert-butyl to tris(3,5-xylyl)silyl on the phenolate moiety. Complexes with a triphenylsilyl substituent on the naphtholate moiety displayed good catalytic activity in the hydroamination/cyclization of aminoalkenes, while complexes with a methyldiphenylsilyl substituent exhibited somewhat lower reactivity. The highest enantioselectivities for five- and six-membered-ring formation were observed utilizing complex 9c-Lu (R¹ = Ph, R ² = Me, R³ = SiPh₃) in the cyclization of (2,2-diphenylpent-4-enyl)amine (92% ee, N_t = 200 h^-1 at 25 C) and (2,2-diphenylhex-5-enyl)amine (73% ee, N_t = 20 h^-1 at 25 C). The complexes can be applied in asymmetric intermolecular hydroaminations of 1-heptene and 4-phenyl-1-butene with benzylamine with enantioselectivities of up to 40% ee using complex 9b-Y (R¹ = Ph, R² = Me, R³ = SiPh₂Me). Here the higher catalytic activities are achieved with catalysts having a methyldiphenylsilyl substituent on the naphtholate moiety. Lanthanum aminodiolate catalysts generated in situ from [La{CH(C₆H₅)NMe₂} ₃] did not exhibit improved catalytic activity in the intermolecular hydroamination in comparison to the corresponding yttrium and lutetium catalysts. The overall catalytic activities of the aminodiolate complexes are somewhat diminished in comparison to previously studied binaphtholate complexes due to the presence of the additional amine donor site in the ligand framework.

Full text of DOI:10.1021/om3010614

Article
pubs.acs.org/Organometallics
C1‑Symmetric Rare-Earth-Metal Aminodiolate Complexes for Intra-
and Intermolecular Asymmetric Hydroamination of Alkenes
Alexander L. Reznichenko and Kai C. Hultzsch*
Department of Chemistry & Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New
Jersey 08854-8087, United States
S
* Supporting Information
ABSTRACT: A series of novel C1-symmetric aminodiolate
rare-earth-metal complexes have been prepared via arene
elimination from [Ln(o-C6H4CH2NMe2)3] (Ln = Y, Lu) and
the corresponding aminodiol proligand. The NOBIN-derived
aminodiolate ligands feature sterically demanding triphenylsilyl
and methyldiphenylsilyl ortho substituents on the naphtholate
moiety and substituents of varying steric demand ranging from
tert-butyl to tris(3,5-xylyl)silyl on the phenolate moiety.
Complexes with a triphenylsilyl substituent on the naphtholate
moiety displayed good catalytic activity in the hydroamination/
cyclization of aminoalkenes, while complexes with a methyldiphenylsilyl substituent exhibited somewhat lower reactivity. The
highest enantioselectivities for five- and six-membered-ring formation were observed utilizing complex 9c-Lu (R1 = Ph, R2 = Me,
R3 = SiPh3) in the cyclization of (2,2-diphenylpent-4-enyl)amine (92% ee, Nt = 200 h−1 at 25 °C) and (2,2-diphenylhex-5-
enyl)amine (73% ee, Nt = 20 h−1 at 25 °C). The complexes can be applied in asymmetric intermolecular hydroaminations of 1-
heptene and 4-phenyl-1-butene with benzylamine with enantioselectivities of up to 40% ee using complex 9b-Y (R1 = Ph, R2 =
Me, R3 = SiPh2Me). Here the higher catalytic activities are achieved with catalysts having a methyldiphenylsilyl substituent on the
naphtholate moiety. Lanthanum aminodiolate catalysts generated in situ from [La{CH(C6H5)NMe2}3] did not exhibit improved
catalytic activity in the intermolecular hydroamination in comparison to the corresponding yttrium and lutetium catalysts. The
overall catalytic activities of the aminodiolate complexes are somewhat diminished in comparison to previously studied
binaphtholate complexes due to the presence of the additional amine donor site in the ligand framework.
tions have been developed,12,13 but only a few of these catalysts
INTRODUCTION
■
achieve enantioselectivities exceeding 90% ee.12r,u,13d Our group
The development of efficient synthetic protocols for the
has previously studied rare-earth-metal binaphtholate complexes
synthesis of nitrogen-containing molecules is an area of intense
I-Ln (Chart 1), which are among the most active and most
research, thanks to their importance as bulk chemicals, specialty
stereoselective catalysts for hydroamination/cyclization of
chemicals, and pharmaceuticals.1 The hydroamination reaction
aminoalkenes.13b,d These catalysts have also been successfully
offers a waste-free, highly atom efficient, and green pathway to
applied in the kinetic resolution of racemic aminoalkenes,13b,d,e
produce amines, enamines, and imines via the catalyzed addition
and they have remained so far the only catalysts to achieve
of amines to unsaturated carbon−carbon bonds.2−6 Most alkene
stereocontrolled intermolecular hydroaminations of unactivated
hydroamination studies have focused on the intramolecular
alkenes with simple amines.10b Although the latter trans-
reaction, while studies of the intermolecular process are relatively
formation catalyzed by I-Ln shows the general feasibility of the
scarce. The intermolecular hydroamination of activated alkenes,
approach itself, it still requires rather forcing reaction conditions
such as vinyl arenes, norbornene derivatives, conjugated dienes,
and suffers from moderate selectivity and a need to employ a
large (10−15-fold) excess of alkene. It may be envisioned that at
least some of these drawbacks result from the high Lewis acidity
and allenes, is significantly more facile7,8 than the addition of
amines to simple, unactivated alkenes.9,10
The generation of new stereogenic centers during the C−N
of the electron-deficient binaphtholate complex I-Ln that leads
bond forming process has been an area of particular interest, but
to a stronger binding of exogenous amine molecules to the metal
the development of chiral catalysts for the asymmetric
center and coincidental diminished catalytic activity.
The diamino bis(thiophenolate) complexes II reported by
Livinghouse and co-workers achieved high enantioselectivities
hydroamination of alkenes (AHA) has remained quite
challenging,8,10−14 especially for intermolecular reactions.8,10
Rare-earth-metal complexes are among the most active
hydroamination catalysts for a broad spectrum of hydro-
Special Issue: Recent Advances in Organo-f-Element Chemistry
amination substrates, including alkenes, alkynes, conjugated
dienes, and allenes.2,3a,b A variety of chiral rare-earth-metal
Received: November 7, 2012
catalysts for asymmetric intramolecular hydroamination reac-
Published: January 29, 2013
© 2013 American Chemical Society
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Chart 1. Rare-Earth-Metal Hydroamination Catalysts with X2
(I), L2X2 (II), and LX2 Type Ligands (III)
Figure 1. Generic design for NOBIN-derived rare-earth-metal amino-
diolate complexes.
performed in a single pot and do not require product isolation.
The well-documented literature procedure for the multigram-
scale preparation of compound 118 starting from BINOL in 88%
yield over four steps represents one of the most concise routes to
chiral NOBIN ligands.19 Removal of the MOM group from 3a,b
required protection of the amino group, which was otherwise
hampering the acid-catalyzed hydrolysis of the acetal under
conditions compatible with acid-sensitive silyl groups. Sub-
sequently, the trifluoroacetyl group was easily removed with
NaBH4 to give the silylated NOBIN derivatives 4a,b.
The amino alcohols 4 can be condensed with variously
substituted salicylaldehydes 520 utilizing typical salen coupling
methodology. The resulting Schiff bases were subsequently
reduced to the salan-type aminodiols 6 with lithium aluminum
hydride. The attempted reductive amination of amines 6 with
formaldehyde led to an unexpected result, as a redox-neutral
cyclization to the cyclic aminals 7 proceeded cleanly instead of
formation of the anticipated N-methyl derivative 8. However, the
latter were obtained via reduction of the somewhat air-sensitive
aminals 7 with lithium aluminum hydride. Attempts to introduce
larger alkyl substituents on nitrogen via reductive amination of
other aldehydes, e.g. benzaldehyde, have been plagued by low
yields and were not explored further.
A number of NOBIN-based aminodiol proligands 8, such as
the 3-triphenylsilyl-substituted 8a−f and the 3-methyldiphenyl-
silyl-substituted 8g−h, were obtained using this methodology.
Complex Synthesis. With the aminodiol proligands 8a−h in
hand, we proceeded with the synthesis of the corresponding
yttrium and lutetium aminodiolate complexes using the well-
known tris(aryl) rare-earth-metal precursors [Ln(o-
C6H4CH2NMe2)3] (Ln = Y, Lu)21 (Scheme 2).
(up to 89% ee) for a broad range of aminoalkene substrates.12g
Unfortunately, these catalysts exhibit diminished catalytic activity
in comparison to complexes I and require prolonged reaction
times at ambient temperatures. Thus, it appears that the reduced
reactivity of complexes II results from an electronic over-
saturation of the metal center by the L2X2-type diamino
bis(thiophenolate) ligands in comparison to the X2-type
binaphtholate ligands in I. Previous studies in our group have
shown that complexes containing (achiral) tridentate diamido-
amine ligands exhibit excellent catalytic activity at ambient
temperature,15 which suggests that spectator ligands of the
general LX2 type provide an electronic environment favorable for
catalytic hydroamination. We therefore envisioned that a catalyst
system incorporating a chiral LX2 type ligand should possess
good catalytic activity, while the larger bite angle of the ligand
should provide an opportunity for improved control of
stereoselectivity.
The arene elimination proceeded smoothly at room temper-
ature or slightly elevated temperature. The yttrium complexes 9-
Y were obtained for the whole family of proligands 8a−h, while
lutetium complexes were only prepared from 8a,c−f. Although
the reactions proceeded cleanly by NMR spectroscopy (see the
Supporting Information), removal of traces of free N,N-
dimethylbenzylamine proved to be difficult in preparative-scale
reactions.22 Therefore, the catalysts were generally prepared in
situ or stored as a frozen stock solution in C6D6 at −30 °C and
were then used directly in catalytic reactions without isolation.
Complexes 9-Ln did not show any noticeable decomposition
after heating to 150 °C for 1 h in solution, but the isolated solid
catalysts were found to decompose above 60 °C.
Herein we present our studies on the synthesis of novel chiral
C1-symmetric rare-earth-metal aminodiolate complexes and their
application in asymmetric intra- and intermolecular hydro-
aminations of unactivated alkenes with simple amines.
RESULTS AND DISCUSSION
■
Ligand Design and Preparation. As the potential model
system, we chose the chiral C1-symmetric NOBIN-derived
aminodiolate complexes IV (Figure 1).16,17 On the basis of
previous experience, we decided to incorporate sterically
demanding substituents in the ortho position of the aryloxide
groups in order to prevent catalyst aggregation,13a,c,17 increase
catalytic activity,13d and improve stereoselectivity.13d Thus, the
ability to easily tune the ortho substituents R1 and R3 is important
to adapt the catalyst design successfully.
The 1H and 13C NMR spectra of complexes 9a−h reflect their
highly unsymmetric structure, giving rise to the maximum
number of possible signals. Both methylene protons of the ortho-
metalated N,N-dimethylbenzylamine ligand as well as both N-
methyl groups are diastereotopic, indicating tight binding of the
The silylated NOBIN derivatives 4a,b were chosen as key
precursors for the diol proligand preparation. 4a,b were
synthesized from the O,N-bis-protected NOBIN derivative 1
according to Scheme 1 in six steps, several of which can be
1
amino group on the NMR time scale. The H NMR spectra of
the complexes display broad features at room temperature, which
may be caused by hindered rotation of the sterically demanding
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Scheme 1. Synthesis of NOBIN-Derived Aminodiol Proligands 8a−h
protection from the tridentate ligand framework. Another
important observation was the steric versatility of the diolate
complexes accessible via the arene elimination route depicted in
Scheme 2. The steric demand ranges from the highly hindered
complexes 9c−e to the sterically significantly less hindered
complex 9g-Y, which features a methyldiphenylsilyl and a tert-
butyl substituent. This should be compared to tert-butyl-
substituted biphenolate complexes that form dimeric species13a,c
and thermally unstable methyldiphenylsilyl-substituted binaph-
tholate arene complexes.23 This broader scope in tolerated ortho
substituents can presumably be attributed to the increased ligand
denticity and bite angle of the NOBIN-derived aminodiolate
ligands 8 in comparison to the binaphtholate ligands in
complexes I.
Scheme 2. Preparation of Rare-Earth-Metal Aminodiolates 9
While a monomeric structure of the aminodiolate complexes 9
could not be proven unambiguously in the absence of
crystallographic structure analysis, there is ample evidence to
suggest that the complexes are indeed monomeric, as shown in
Scheme 2. The complexes exhibit good solubility in aromatic
solvents, whereas dimeric binaphtholate complexes tend to have
low solubility.13a,c The yttrium complexes exhibit a clean doublet
signal in the 13C{1H} NMR spectrum for the ipso carbon of the
ortho-metalated N,N-dimethylbenzylamine ligand, and no
evidence of a coupling to a second yttrium is discernible.
There is also no NMR spectroscopic evidence to support the
presence of a second species (e.g., from a monomer/dimer
equilibrium) similar to previously studied biphenolate complex-
es.13a,c The lack of binding of free N,N-dimethylbenzylamine
underlines the increased steric hindrance and electronic donation
from the aminodiolate ligands to the metal, in comparison to
ortho substituents on the phenolate and naphtholate moieties.
The aminodiolate complexes 9a−h do not retain a coordinated
molecule of N,N-dimethylbenzylaminein contrast to binaph-
1
tholate complexes Ia,baccording to their H and 13C NMR
spectra. This observation is indicative of the reduced Lewis
acidity of 9a−h in comparison to Ia,b as well as increased steric
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Table 1. Catalyst Evaluation of Aminodiolate Complexes in the Hydroamination/Cyclization of 10a
a
a
b
c
d
entry
Ln
Y
ligand
cat./sub, mol %
t, min
Nt, h−1
% ee (confign)
1
(S)-8a
(S)-8a
(S)-8b
(S)-8c
(S)-8c
(S)-8c
(R)-8d
(R)-8d
(S)-8e
(S)-8e
(S)-8f
(S)-8f
(S)-8g
(S)-8h
1
30
30
15
6
200
100
230
400
200
50
17 (S)
48 (S)
6 (S)
2
Lu
Y
2
3
2
4
Y
2.2
1.4
2
27 (S)
e
5
Lu
Sc
Y
15
60
20
40
15
30
15
45
60
75
92 (S)
6
5 (S)
8 (R)
7
2
150
150
200
100
400
130
50
8
Lu
Y
1
4 (R)
9
2
48 (S)
77 (S)
51 (S)
68 (S)
48 (R)
13 (S)
10
11
12
13
14
Lu
Y
2
1
Lu
Y
1
2
Y
2
40
a
The precatalysts were prepared in situ via reaction of a 1:1 mixture of [Ln(o-C6H4CH2NMe2)3] (Ln = Sc, Y, Lu)21 and ligand 8a−h in C6D6. The
b
c
complete conversion to the desired complex was confirmed by NMR spectroscopy. Time for >95% conversion. Overall turnover frequency.
d
e
Determined by 19F NMR spectroscopy of the corresponding Mosher amide. Determined by chiral HPLC of the corresponding N-benzamide.
complexes containing 3,3′-silyl-substituted binaphtholate li-
gands, which are known to form monomeric species.13d
used in complexes Ia,b results in a steric overcrowding around
the smallest rare-earth metal, thus significantly diminishing the
possibility of the scandium catalyst to discriminate the two
diastereomeric cyclization transition states. The highest
enantioselectivity of 92% ee was observed for the lutetium
complex with two triphenylsilyl substituents (Table 1, entry 5).
Interestingly, most S-configured catalysts formed the S
enantiomer of the hydroamination product preferentially,
which is in contrast to the selectivity observed with the
binaphtholate complexes Ia,b.13d However, the yttrium catalyst
based on the sterically least demanding ligand, (S)-8g, produced
11a with the opposite R configuration. Such a reversal of
enantioselectivity within a family of catalysts is not uncommo-
n.12a,b,d,13f
In order to get a deeper insight into the catalytic properties of
the novel catalysts, we investigated the catalytic hydroamination/
cyclization of a broader range of aminoalkenes (Table 2). The
lutetium catalyst 9c-Lu derived from the bis(triphenylsilyl)-
substituted ligand 8c, which had provided the highest selectivity
in the cyclization of 10a, achieved the hydroamination/
cyclization of aminopentenes 10b−d and aminohexene 12 with
moderate enantioselectivities (52−73% ee), but the cyclization
of aminoheptene 14 to form the azepane 15 proceeded in only
27% ee. Interestingly, piperidine 13 was formed in 73% ee, which
is among the highest selectivities reached to date in the
hydroamination of aminohexene substrates (Table 2, entry
20).24 While hydroamination/cyclization of the activated
substrates 10a−c catalyzed by 9c-Lu was only slightly less
efficient than that catalyzed by I-Ln, the unbiased aminopentene
10d required heating to 80 °C to achieve appreciable turnover,
whereas this substrate is cyclized by binaphtholate lutetium
catalysts Ib-Lu at room temperature.13d
Catalytic Intramolecular Hydroamination. For the initial
evaluation of the catalytic activity of complexes 9a−h, formed in
situ from [Ln(o-C6H4CH2NMe2)3] (Ln = Sc, Y, Lu)21 and the
corresponding aminodiol proligand 8a−h, we chose the
aminopentene substrate 10a. Catalysts derived from the
triphenylsilyl-substituted ligands 8a−f showed high turnover
frequencies for the cyclization of aminopentene 10a (Table 1,
entries 1−12). The activity is on the same order of magnitude as
observed for I-Ln.13d The silyl substituent on the phenolate
moiety does not significantly influence the catalytic efficiency,
and the yttrium and lutetium catalysts reached turnover
frequencies in the range of 100−400 h−1 at room temperature.
We were also able to investigate a scandium catalyst derived from
ligand 8c which exhibited a somewhat lower turnover frequency
of 50 h−1 (Table 1, entry 6). However, the sterically less
encumbered yttrium catalysts derived from the methyldiphe-
nylsilyl-substituted ligands 8g,h displayed a somewhat lower
reactivity (Table 1, entries 13 and 14).
The stereoselectivity of the hydroamination/cyclization has a
nonlinear dependence of the steric bulk of the substituent on the
phenolate moiety of the complex. A moderate stereoselectivity is
observed for the yttrium catalyst containing the tert-butyl-
substituted ligand 8a (Table 1, entry 1); however, the slightly
bulkier methyldiphenylsilyl-substituted ligand 8b was less
selective, while the more encumbered yttrium complexes derived
from 8c,e resulted in slightly higher selectivities. The lutetium
complexes exhibited in general a higher selectivity than the
corresponding yttrium congeners, which is in agreement with
previous findings for binaphtholate complexes Ia,b that generally
showed lower selectivities for larger rare-earth metals.13d
However, this trend does not hold true for the smaller scandium
catalyst, which provided almost racemic products (Table 1, entry
6). It seems very likely that the larger bite angle of the
aminodiolate ligand in comparison to the binaphtholate ligands
As expected, scandium was significantly less active than either
lutetium or yttrium (Table 2, entry 6 vs entries 4 and 5 and entry
13 vs entry 12), and in agreement with the results for
aminopentene 10a, it was also shown to be less selective.
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Table 2. Hydroamination/Cyclization of Various Aminoalkenes Catalyzed by Aminodiolate Yttrium, Lutetium, and Scandium
Complexes
a
a
b
c
d
entry
substrate
Ln
Y
ligand
cat./sub, mol %
T, °C
t, h
Nt, h−1
% ee (confign)
1
10b
10b
10b
10b
10b
10b
10b
10b
10b
10b
10c
10c
10c
10c
10c
10c
10d
10d
10d
12
(S)-8a
(S)-8a
(S)-8b
(S)-8c
(S)-8c
(S)-8c
(R)-8d
(R)-8d
(S)-8e
(S)-8e
(S)-8a
(S)-8c
(S)-8c
(R)-8d
(S)-8e
(S)-8e
(S)-8a
(S)-8c
(S)-8f
(S)-8c
(R)-8d
(S)-8c
2
40
40
40
40
40
40
40
40
40
40
25
25
25
25
25
25
80
80
80
25
60
90
4
4
12
12
6
18 (S)
52 (S)
5 (S)
2
Lu
Y
2
3
2
5
4
Y
2
3
15
12
0.4
6
35 (S)
62 (S)
18 (S)
6 (R)
10 (R)
47 (S)
63 (S)
30 (S)
52 (S)
7 (S)
4 (R)
10 (S)
46 (S)
66 (S)
59 (S)
47 (S)
73
5
Lu
Sc
Y
1.4
4
7
6
96
12
12
7
7
2
8
Lu
Y
2
6
9
2
7
10
11
12
13
14
15
16
17
18
19
20
21
22
Lu
Y
2
3
17
110
200
0.7
30
30
25
5
1
0.9
0.6
Lu
Sc
Lu
Y
1.4
2
72
2
1.6
1.5
4
2
Lu
Lu
Lu
Lu
Lu
Y
2
2
10
1.6
50
4
15
1
2
2
2.7
20
150
0.5
12
2
0.33
37
14
Lu
4
51
27
a
The precatalysts were prepared in situ via reaction of a 1:1 mixture of [Ln(o-C6H4CH2NMe2)3] (Ln = Sc, Y, Lu)21 and ligand 8a−h in C6D6. The
b
c
complete conversion to the desired complex was confirmed by NMR spectroscopy. Time to >95% conversion. Overall turnover frequency.
d
Determined by 19F NMR spectroscopy of the corresponding Mosher amide.
Table 3. Catalytic Kinetic Resolution of Chiral Aminopentenes with (S)-9c-Y Prepared in Situ from [Y(o-C6H4CH2NMe2)3] and
(S)-8c
entry
substrate
t, h
conversn, %
trans:cis
ee of recov 16, %
f
1
2
16a
16b
19
20
55
54
≥50:1
9:1
62
46
5.9
3.4
a
For a definition of the resolution factor f see ref 25.
These results suggest that scandium will require a ligand where
the steric demand of the substituents has been adapted more
specifically to the small ionic radius of that element.
The yttrium catalyst containing the bis(triphenylsilyl)-
substituted ligand 8c was also evaluated in the kinetic resolution
of chiral racemic aminoalkenes (Table 3).13b,d,e These substrates
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Table 4. Intermolecular Hydroamination of Terminal Alkenes Catalyzed by Aminodiolate Complexes
a
a
b
c
d
entry
R
Ln
Y
ligand
x
T, °C
t, h
conversn, % (yield, %)
ee, % (confign)
1
2
n-C5H11
(S)-8a
(S)-8a
(S)-8c
(R)-8d
(S)-8h
(S)-8a
(S)-8a
(S)-8b
(S)-8g
(S)-8h
15
15
15
15
15
10
10
10
10
10
150
150
170
170
170
150
150
150
150
150
96
96
85 (62)
75 (62)
trace
36 (R)
7 (R)
n-C5H11
Lu
Y
3
n-C5H11
120
120
90
4
n-C5H11
Y
trace
5
n-C5H11
Y
70 (53)
80 (67)
75 (61)
70 (52)
80 (63)
85 (66)
4 (S)
6
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
PhCH2CH2
Y
76
17 (R)
9 (R)
7
Lu
Y
96
8
96
40 (R)
20 (R)
5 (R)
9
Y
50
10
Y
48
a
The precatalysts were prepared in situ via reaction of a 1:1 mixture of [Ln(o-C6H4CH2NMe2)3] (Ln = Y, Lu)21 and ligand 8a−d,g,h in C6D6. The
b
c
complete conversion to the desired complex was confirmed by NMR spectroscopy. By 1H NMR spectroscopic analysis. Isolated yield after column
chromatography. Determined by chiral HPLC of the corresponding N-benzamide.
d
Table 5. Lanthanum-Catalyzed Intermolecular Hydroamination of Terminal Alkenes
a
b
c
d
entry
ligand
T, °C
t, h
conversn, % (yield, %)
ee, % (confign)
1
2
3
4
(S)-8a
(S)-8c
(R)-8d
(S)-8h
170
150
150
170
48
96
trace
85 (61)
90 (66)
trace
38 (R)
28 (S)
120
48
a
b
The precatalysts were prepared in situ via reaction of a 1:1 mixture of [La{CH(C6H5)NMe2}3]26 and ligand 8a,c,d,h in C6D6. By H NMR
1
c
d
spectroscopic analysis. Isolated yield after column chromatography. Determined by chiral HPLC of the corresponding N-benzamide.
were previously cyclized by the binaphtholate catalysts I-Ln with
resolution factors25 of up to 19 for 16a and 6 for 16b.13b,d,e In line
with the observed reversal of enantioselectivity in the hydro-
amination/cyclization of achiral aminoalkenes in comparison to
the selectivity observed for I-Ln, the reisolated, slower reacting
enantiomer of aminoalkenes 16a,b obtained in the resolution
with (S)-9c-Y had an S configuration, which is the opposite
selectivity observed for I-Ln.
Intermolecular Asymmetric Hydroamination. On the
basis of the catalytic results obtained in the intramolecular
hydroaminations, we were optimistic that intermolecular
asymmetric hydroamination may be attainable with these novel
aminodiolate complexes as well. Indeed, we found that the
aminodiolate complexes 9 catalyze the addition of benzylamine
to 1-heptene and 4-phenyl-1-butene, leading exclusively to the
Markovnikov products (Table 4) under conditions comparable
to those used for complexes I. The S-configured catalysts
generally produce the R product enantiomers, which is again
opposite to the selectivity pattern observed for the binaphtholate
complexes I.
plexes 9c-Y and 9d-Y, which have silyl substitution patterns
similar to those of binaphtholate complexes Ia-Y and Ib-Y,
respectively. For the complexes with a triphenylsilyl substituent
on the naphtholate moiety, only the least encumbered complexes
with tert-butyl (derived from ligand 8a) and methyldiphenylsilyl-
substituents (derived from ligand 8b) on the phenolate moiety
were catalytically active. However, yttrium complexes prepared
from the sterically less demanding ligands 8g,h with methyl-
diphenylsilyl substituents on the naphtholate moiety displayed
higher reactivity (Table 4, entries 9 and 10) comparable in
magnitude to that of I-Ln. Unfortunately, the selectivity drops
significantly when the steric bulk is decreased, and only 40% ee
was achieved for the secondary amine 18b using 9b-Y (Table 4,
entry 8). Similar to the reactivity of complexes 9 in the
intramolecular hydroamination, the increased denticity and
larger bite angle of the aminodiolate ligand is favorable for
utilizing midsized tert-butyl and methyldiphenylsilyl substituents
in the intermolecular hydroamination; neither of these
substituents were suitable to form viable monomeric diolate
hydroamination catalysts.13a,c,23
The aminodiolate complexes were less reactive than complex
Ia-Y,10b and the reactivity drops significantly with increasing
steric bulk of the ligand. Thus, no reactivity was observed for the
sterically encumbered bis(trisaryl)silyl-substituted yttrium com-
Lanthanum Catalysts for Intermolecular Hydroamina-
tion. The catalytic activity of rare-earth-metal-based hydro-
amination catalysts generally increases with increasing size of the
metal ionic radius. Therefore, we were anticipating that
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lanthanum aminodiolate complexes should also perform better
than their smaller yttrium and lutetium congeners. Unfortu-
nately, attempts to prepare aminodiolate lanthanum amido
complexes via amine elimination from the lanthanum tris(amide)
[La{N(SiMe3)2}3] and the proligand 8 did not produce a well-
defined species and the crude reaction mixtures were catalytically
inactive in the intermolecular hydroamination. While the
lanthanum tris(aryl) complex [La(o-C6H4CH2NMe2)3] is
unavailable, we decided to utilize its constitutional isomer
[La{CH(C6H5)NMe2}3], which has been recently introduced by
Behrle and Schmidt.26 Indeed, treatment of [La{CH(C6H5)-
NMe2}3] with the appropriate proligand 8 generated a species
that was catalytically active in the intermolecular hydroamination
(Table 5). The 1H NMR spectra of the crude reaction mixtures in
toluene-d8 showed broad signals even at −80 °C, presumably due
to the fluxional character of the (dimethylamino)benzyl
lanthanum moiety.26
It appears that the larger lanthanum indeed demands a
different level of steric protection for catalytic activity in
intermolecular hydroamination. While the triphenylsilyl-sub-
stituted yttrium complexes derived from 8c,d were catalytically
inactive, the corresponding lanthanum aminodiolate complexes
were catalytically active. Lanthanum complexes prepared from
the sterically less demanding ligands 8a,h produced only traces of
hydroamination product. The lanthanum catalyst based on
ligand 8c produced the hydroamination product 18b in 38% ee
(Table 5, entry 2). The activity and selectivity of this complex is
quite comparable to those of the yttrium catalysts utilizing
ligands 8a,b (Table 4, entries 1 and 8). Hence, it appears that
contrary to general wisdom in hydroamination catalysis,2,3a,b the
larger lanthanum metal did not significantly improve catalytic
activity for intermolecular hydroamination.
enantioselectivity of the intramolecular hydroamination as well
as the reactivity in the intermolecular hydroamination are
critically dependent on the steric features of the ligand
framework. The steric requirements for the ligand set seem to
be different in intramolecular and intermolecular hydroamina-
tion reactions. In order to achieve more efficient intermolecular
hydroaminations and allow a more rational catalyst design, it will
be important to better understand these steric and electronic
factors that influence catalytic performance.
EXPERIMENTAL SECTION
■
General Considerations. All reactions with air- or moisture
sensitive materials were performed in oven (120 °C) and flame-dried
glassware under an inert atmosphere of argon, employing standard
Schlenk and glovebox techniques. Alkenes and C6D6 were distilled from
sodium/benzophenone ketyl. Amines and aminoalkenes were distilled
twice from finely powdered CaH2. DMF was distilled from CaH2. All
other commercially available starting materials were used as received.
1H, 13C{1H}, and 19F NMR spectra were recorded on Varian (400 and
500 MHz) spectrometers at 25 °C unless stated otherwise. Chemical
shifts are reported in ppm downfield from tetramethylsilane with the
nondeuterated portion of the solvent as internal standard. Mass spectra
were recorded on a Finnigan LCQ-DUO mass spectrometer. Silica gel
(230−400 mesh, Sorbent Technologies) and alumina (80−200 mesh,
EMD) were used for column chromatography. Elemental analyses were
performed by Robertson Microlit Laboratories, Inc., Ledgewood, NJ.
(S)-Mosher acid was transformed into the corresponding (R)-
Mosher acid chloride according to a literature protocol.27 N,N-Dibenzyl-
N-[2′-(methoxymethoxy)-1,1′-binaphthalen-2-yl]amine (1),18 3,5-di-
tert-butylsalicylaldehyde (5a),28 and silyl-substituted salicylaldehydes
5b,c,e,f,29 as well as the rare-earth-metal precursors [Ln(o-
C6H4CH2NMe2)3] (Ln = Sc, Y, Lu),21 and [La{CH(C6H5)NMe2}3],26
were prepared according to literature protocols. The aminoalkene
substrates (2,2-diphenylpent-4-enyl)amine (10a),12d (2,2-dimethyl-
pent-4-enyl)amine (10b),30a (1-allylcyclohexyl)methylamine (10c),30b
pent-4-en-1-ylamine (10d),30c (2,2-diphenylhex-5-enyl)amine (12),30d
(2,2-diphenylhept-6-enyl)amine (14),30e (1-phenylpent-4-en-1-yl)-
amine (16a),13d and (1-cyclohexylpent-4-en-1-yl)amine (16b)13e were
synthesized according to literature protocols. The hydroamination
products 2-methyl-4,4-diphenylpyrrolidine (11a),12d 2,4,4-trimethyl-
pyrrolidine (11b),30c 3-methyl-2-azaspiro[4.5]decane (11c),12h 2-
methylpyrrolidine (11d),30c 2-methyl-5,5-diphenylpiperidine (13),12d
2-methyl-6,6-diphenylazepane (15),14l,30f 2-methyl-5-phenylpyrrolidine
(17a),13d 2-cyclohexyl-5-methylpyrrolidine (17b),13e N-benzylheptan-
2-amine (18a),10b,31 and N-benzyl-4-phenylbutan-2-amine (18b)10b,31
are known compounds and were identified by comparison to the
literature NMR spectroscopic data. Catalytic intramolecular hydro-
amination reactions of aminoalkenes and kinetic resolution experiments
were performed as previously reported.13d,e The absolute configuration
of the hydroamination/cyclization products was determined by
comparison of the 19F NMR spectroscopic data of the Mosher amides
with the assignments reported previously.13d
SUMMARY
■
A new family of C1-symmetric NOBIN-derived aminodiolate
diolate complexes 9-Ln featuring various degrees of steric
protection were synthesized. The complexes were shown to be
catalytically active in intra- and intermolecular asymmetric
hydroaminations of unactivated alkenes. The most active systems
can reach catalytic activity comparable in magnitude toor only
slightly lower thanthe binaphtholate complexes I in the case of
intramolecular hydroamination of the Thorpe−Ingold-activated
aminoalkenes 10a−c and 12 with complexes 9a−f and in
intermolecular hydroaminations with catalysts 9g-Y and 9h-Y.
The slightly diminished catalytic activity of catalysts 9-Ln in
comparison to I-Ln can be attributed to the additional amine
donor site in the aminodiolate ligand framework. The broad
spectrum of substituents tolerated in the precatalysts allowed us
to observe the highest and lowest acceptable level of steric bulk
required for catalytic activity with midsized (Lu, Y) and large
(La) rare-earth metals. The hydroamination of aminopentenes
and aminohexenes proceeded with enantioselectivities of up to
92 and 73% ee, respectively. Scandium was significantly less
active and less enantioselective in intramolecular hydroamina-
tion reactions utilizing the bis(triphenylsilyl)-substituted ligand
8c, suggesting that this ligand is too crowded for the smallest
rare-earth metal. The intermolecular hydroamination of simple
terminal alkenes with benzylamine was achieved with enantio-
selectivities of up to 40% ee, which is slightly lower than the
selectivities observed previously for binaphtholate catalysts I. In
addition, several lanthanum-based hydroamination catalysts
were applied in the intermolecular hydroamination as well and
enantioselectivities of up to 38% ee were achieved. The
Chlorotris(3,5-xylyl)silane.32 To a solution of 5-bromo-m-xylene
(11.1 g, 60.0 mmol) in Et2O (75 mL) was added dropwise n-BuLi (1.6
M in hexanes, 37.5 mL, 60.0 mmol) at 10 °C. After 4 h at this
temperature, SiCl4 (2.3 mL, 3.40 g, 20.0 mmol) was added dropwise at
−10 °C. The resulting mixture was warmed to room temperature and
stirred overnight. The solvent was removed in vacuo, and the residue
was extracted with warm toluene (2 × 20 mL). The combined extracts
were concentrated in vacuo, and the residue was recrystallized from
hexanes. After filtration, 3.48 g (47% yield) of the target product was
obtained in the form of white crystals. 1H NMR (400 MHz, CDCl3): δ
7.24 (s, 6H), 7.10 (s, 3H, aryl-H), 2.31 (s, 18H, 6 CH3). 13C{1H} NMR
(CDCl3, 75 MHz): δ 137.4, 132.9, 132.8, 132.4 (aryl), 21.4 (CH3).
General Procedure for the Synthesis of 2 via Silylation of
Protected NOBIN Derivative 1. To a stirred solution of 1 (4.58 g, 9.0
mmol) in Et2O (80 mL) was added dropwise n-BuLi (2.5 M in hexanes,
4.7 mL, 11.7 mmol) at 0 °C. The mixture was stirred at this temperature
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for 5 h and then for 2 h at room temperature and was then cooled to −30
°C. THF (50 mL), a solution of the chlorosilane (11.7 mmol) in THF
(10 mL), and HMPA (3.0 mL, 12 mmol) were added to the solution in
that order. The dark brown solution was warmed to room temperature
slowly and was stirred overnight. The mixture was quenched with a
saturated ammonium chloride solution (100 mL), and the product was
extracted with dichloromethane (2 × 50 mL). The combined organic
extracts were dried (Na2SO4) and concentrated. The residue was
purified by column chromatography.
(aryl), 97.8 (CH2), 56.1 (CH3O), −2.9 (SiCH3). MS (ESI): m/z 526.2
[M + H]+.
General Procedure for the Deprotection of Acetal 3. To a
stirred solution of 3 (3.4 mmol) and Et3N (0.71 mL, 5.0 mmol) in
dichloromethane (20 mL) was added dropwise trifluoroacetic anhydride
(0.53 mL, 4.0 mmol) at 0 °C. The mixture was stirred at room
temperature for 2 min, washed with 1 M HCl (5 mL), and concentrated
in vacuo. The residue was dissolved in dioxane (10 mL), and 12 M HCl
(1 mL) was added. The mixture was stirred overnight at 65 °C. The
mixture was neutralized with a saturated NaHCO3 solution, and the
product was extracted with ethyl acetate (2 × 75 mL). The combined
organic extracts were dried (Na2SO4), and the solvent was evaporated.
The residue was dissolved in ethanol (10 mL) and treated with NaBH4
(0.34 g, 10 mmol). The mixture was stirred at room temperature
overnight and was quenched by addition of 2% KOH solution (50 mL).
The product was extracted with dichloromethane (2 × 50 mL). The
combined organic extracts were dried (Na2SO4) and passed through a
short silica plug, and the solvent was evaporated to give 4.
N,N-Dibenzyl-N-[2′-(methoxymethoxy)-3′-(triphenylsilyl)-1,1′-bi-
naphthalen-2-yl]amine (2a). Purified by column chromatography on
silica (hexanes/toluene 1/1) to give 4.50 g (65%) of 2a as a white solid.
1H NMR (500 MHz, CDCl3): δ 7.88 (s, 1H), 7.71 (d, 3J(H,H) = 8.8 Hz,
1H), 7.68 (d, 3J(H,H) = 7.8 Hz, 1H), 7.63 (d, 3J(H,H) = 8.3 Hz, 1H),
7.57 (d, 3J(H,H) = 7.8 Hz, 6H, SiPh3), 7.30−7.10 (m, 14H), 7.05 (vt,
3J(H,H) = 8.1, 7.1 Hz, 1H), 7.00−6.89 (m, 7H), 6.85−6.80 (m, 4H, aryl-
2
H), 3.94 (m, 5H, 2CH2Ph, CH2O), 3.65 (d, 1H, J(H,H) = 5.1 Hz,
CH2O), 2.04 (s, 3H, CH3). 13C{1H} NMR (125 MHz, CDCl3): δ 157.4,
148.7, 141.2, 138.4, 136.5, 135.9, 135.09, 135.06, 130.3, 130.1, 129.3,
126.0, 125.1, 124.5, 124.1, 122.8, 97.4 (CH2O), 56.6 (CH3), 55.8
(CH2Ph).
2′-Amino-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (4a). White
1
solid, 90% yield. H NMR (400 MHz, CDCl3): δ 7.90 (s, 1H), 7.79
(d, 3J(H,H) = 9.0 Hz, 1H), 7.78−7.72 (m, 2H), 7.67 (d, 3J(H,H) = 8.2
Hz, 6H), 7.43−7.34 (m, 8H), 7.30−7.19 (m, 6H), 7.14−7.11 (m, 1H),
7.09 (d, 3J(H,H) = 9.0 Hz, 1H, aryl-H), 5.29 (s, 1H, OH), 3.76 (br s, 2H,
NH2). 13C{1H} NMR (100 MHz, CDCl3): δ 155.6 (CO), 143.7, 141.2,
136.3, 134.6, 134.0, 130.5, 129.4, 129.2, 123.5, 123.4, 122.7, 118.1, 113.7,
108.6 (aryl).
N,N-Dibenzyl-N-[2′-(methoxymethoxy)-3′-(methyldiphenylsilyl)-
1,1′-binaphthalen-2-yl]amine (2b). Purified by column chromatog-
raphy on silica (hexanes/DCM 5/3) to give 4.13 g (65%) of 2b as a
1
white solid. H NMR (500 MHz, CDCl3): δ 7.86 (s, 1H), 7.83 (d,
3J(H,H) = 8.8 Hz, 1H), 7.79 (d, 3J(H,H) = 8.1 Hz, 1H), 7.73 (d, 3J(H,H)
= 8.3 Hz, 1H), 7.61 (d, 3J(H,H) = 7.3 Hz, 2H), 7.55 (d, 3J(H,H) = 7.3
Hz, 2H), 7.44−7.29 (m, 9H), 7.21−7.10 (m, 9H), 7.00 (d, 3J(H,H) = 8.6
Hz, 1H), 6.92 (dd, 3J(H,H) = 7.6 Hz, 4J(H,H) = 2.0 Hz, 4H, aryl-H),
4.05 (d, 2J(H,H) = 14.4 Hz, 2H, PhCH2N), 3.99 (d, 2J(H,H) = 4.7 Hz,
1H, CH2O), 3.95 (d, 2J(H,H) = 4.7 Hz, 1H, CH2O), 3.89 (d, 2J(H,H) =
14.4 Hz, 2H, PhCH2N), 2.33 (s, 3H, CH3O), 0.96 (s, 3H, SiCH3).
13C{1H} NMR (125 MHz, CDCl3): δ 157.2 (CO), 148.9, 139.9, 138.5,
2′-Amino-3-(methyldiphenylsilyl)-1,1′-binaphthalen-2-ol (4b).
1
Off-white solid, 83% yield. H NMR (500 MHz, DMSO-d6): δ 8.19
(s, 1H), 7.75−7.69 (m, 4H), 7.56 (d, 3J(H,H) = 6.7 Hz, 4H), 7.41−7.33
(m, 6H), 7.22−7.20 (m, 2H), 7.16 (d, 3J(H,H) = 8.8 Hz, 1H), 7.12−7.06
(m, 2H), 6.93 (m, 1H), 6.79 (d, 3J(H,H) = 7.3 Hz, 1H, aryl-H), 4.69 (br
s, 2H, NH2), 0.92 (s, 3H, SiCH3). 13C{1H} NMR (125 MHz, DMSO-
d6): δ 157.1 (CO), 144.9, 138.4, 136.8, 136.7, 134.9, 134.8, 134.7, 134.4,
133.9, 129.08, 129.05, 129.0, 128.3, 127.9, 127.72, 127.68, 127.4, 126.9,
125.84, 125.81, 124.0, 123.0, 120.7, 118.7, 113.8, 108.5 (aryl), −2.9
(SiCH3).
137.3, 136.7, 145.6, 135.5, 135.1, 135.0, 130.9, 130.4, 130.2, 129.3, 129.2,
128.9, 128.5, 128.3, 127.9, 127.82, 127.78, 127.7, 127.6, 127.1, 126.6,
126.3, 126.2, 126.1, 125.5, 124.5, 124.2, 122.7 (aryl), 97.8 (CH2O), 56.6
(CH3O), 56.0 (CH2Ph), −3.0 (SiCH3).
General Procedure for the Synthesis of Salicylaldehydes
5d,e. In a procedure that was adopted from ref 29, KH (400 mg, 10.0
mmol) was added slowly to a solution of 2,6-dibromo-4-methylphenol
(5.00 mmol) in THF (25 mL) at 0 °C. After the mixture was stirred for
30 min, the appropriate chlorosilane (5.00 mmol) was added in one
portion. The reaction mixture was heated to reflux for 16−48 h
(monitored by TLC). The solvent was then removed in vacuo and the
residue diluted with hexanes (100 mL) and water (50 mL). The layers
were separated, and the organic layer was washed with aqueous HCl (0.2
N, 30 mL), water (30 mL), and brine (30 mL). The solution was then
dried (Na2SO4) and concentrated in vacuo. The crude silyl ethers were
used directly in the next step without further purification.
General Procedure for the Synthesis of 3 via Debenzylation
of Amine 2. To a stirred suspension of 2 (4.60 mmol) in absolute
ethanol (150 mL) was added ammonium formate (5.00 g, 80 mmol) and
10% Pd on charcoal (1.20 g, 0.23 mmol), and the mixture was refluxed
for 2 days. Caution! Condensation of ammonium salts in a reflux
condenser may result in an isolated overpressured system. The mixture
was cooled and filtered through Celite, and the filtrate was concentrated
in vacuo and treated with 2% KOH solution (100 mL). The product was
extracted with dichloromethane (2 × 100 mL). The combined organic
extracts were dried (Na2SO4), and the solvent was evaporated. The
residue was purified by flash chromatography.
A solution of silyl ether (1.50 mmol) in Et2O (3.0 mL) was cooled to
−78 °C, and then t-BuLi (1.7 M in pentane, 3.53 mL, 6.00 mmol) was
added dropwise. The dark red reaction mixture was stirred for 1.5 h with
warming to 0 °C. The mixture was then cooled to −78 °C and DMF
(0.465 mL, 6.00 mmol) was added in one portion. The reaction mixture
was warmed to 0 °C and was then quenched with saturated aqueous
NH4Cl (5.0 mL) and diluted with EtOAc (75 mL). The layers were
separated, and the organic layer was washed with H2O (2 × 15 mL) and
brine (25 mL), dried (Na2SO4), and concentrated in vacuo to afford the
crude salicylaldehyde 5. Flash chromatography (silica gel, EtOAc/
hexanes, DCM/hexanes, or benzene/hexanes) afforded the pure
salicyladehyde 5.
2-Hydroxy-5-methyl-3-[tris(3,5-dimethylphenyl)silyl]-
benzaldehyde (5d). White solid, purified by flash chromatography on
silica (hexanes/DCM 3/1), 48% yield. 1H NMR (500 MHz, C6D6): δ
11.81 (s, 1H, CHO), 9.21 (s, 1H, OH), 7.70−7.68 (m, 7H), 6.91 (s,
3H), 6.62 (s, 1H, aryl-H), 2.10 (s, 18 H, 6 CH3), 1.86 (s, 3H, CH3).
13C{1H} NMR (125 MHz, C6D6): δ 196.5 (CHO), 165.3 (CO), 147.1,
2′-(Methoxymethoxy)-3′-(triphenylsilyl)-1,1′-binaphthalen-2-
amine (3a). Purified on a short silica column (hexanes/DCM 1/1) to
give 2.01 g (75%) of 3a as a white solid. 1H NMR (400 MHz, CDCl3): δ
7.95 (s, 1H), 7.77 (d, 3J(H,H) = 8.6 Hz, 1H), 7.78−7.73 (m, 2H), 7.67
(d, 3J(H,H) = 7.8 Hz, 6H), 7.43−7.30 (m, 12H), 7.26−7.16 (m, 3H),
7.07 (d, 3J(H,H) = 8.6 Hz, 1H, aryl-H), 3.91 (d, 1H, 2J(H,H) = 5.1 Hz,
CH2O), 3.87 (d, 1H, 2J(H,H) = 5.1 Hz, CH2O), 3.7 (br s, 2H, NH2),
2.20 (s, 3H, CH3). 13C{1H} NMR (100 MHz, CDCl3): δ 158.0, 142.6,
141.1, 136.5, 135.0, 134.9, 134.3, 130.6, 129.49, 129.45, 124.4, 122.2,
121.7, 118.0, 114.0 (aryl), 97.4 (CH2), 55.6 (CH3). MS (ESI): m/z
587.9 [M + H]+.
2′-(Methoxymethoxy)-3′-(methyldiphenylsilyl)-1,1′-binaphtha-
len-2-amine (3b). Purified on a short silica column (hexanes/DCM 1/
1
1) to give 1.32 g (54%) of 3b as a white solid. H NMR (400 MHz,
CDCl3): δ 7.88 (s, 1H), 7.78−7.73 (m, 3H), 7.64−7.62 (m, 4H), 7.41−
7.31 (m, 7H), 7.29−7.27 (m, 2H), 7.23−7.20 (m, 2H), 7.11 (m, 1H),
7.07 (d, 3J(H,H) = 9.0 Hz, 1H, aryl-H), 4.21 (d, 1H, 2J(H,H) = 4.6 Hz,
CH2O), 4.14 (d, 1H, 2J(H,H) = 4.6 Hz, CH2O), 3.70 (br s, 2H, NH2),
2.46 (s, 3H, CH3O), 1.03 (s, 3H, CH3Si). 13C{1H} NMR (125 MHz,
CDCl3): δ 158.0 (CO), 142.5, 140.0, 136.8, 136.8, 135.2, 134.8, 134.2,
133.9, 130.9, 130.7, 129.5, 129.22, 129.20, 128.5, 128.0, 127.9, 127.79,
127.77, 127.4, 126.6, 125.2, 124.8, 124.5, 122.2, 121.8, 118.0, 114.0
137.2, 135.9, 134.9, 134.7, 131.7, 128.6, 124.8, 120.1 (aryl), 21.4 (CH3),
20.1 (CH3).
3-(tert-Butyldiphenylsilyl)-2-hydroxy-5-methylbenzaldehyde (5e).
White solid, purified by flash chromatography on silica (hexanes/
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toluene =2:1−1:1), 80% yield. 1H NMR (400 MHz, CDCl3): δ 11.43 (s,
1H, CHO), 9.89 (s, 1H, OH), 7.56−7.54 (m, 4H), 7.44−7.34 (m, 7H),
7.20 (s, 1H, aryl-H), 2.21 (s, 3H, CH3), 1.21 (s, 9H, t-Bu). 13C{1H}
NMR (75 MHz, CDCl3): δ 196.7 (CHO), 164.4 (CO), 147.7, 136.1,
135.5, 134.8, 129.1, 128.6, 127.6, 124.0, 119.5 (aryl), 29.6 (C(CH3)3),
20.4 (ArCH3), 18.5 (C(CH3)3).
125.0, 124.8, 123.7, 123.66, 123.62, 122.92, 121.78, 120.2, 117.2 (aryl),
79.8 (OCH2), 51.6 (NCH2), 20.5 (ArCH3), −2.6 (SiCH3).
2′-[(3,5-Di-tert-butyl-2-hydroxybenzyl)methylamino]-3-(triphe-
nylsilyl)-1,1′-binaphthalen-2-ol (8a). Prepared from 4a and 5a. White
1
solid, 79% yield. H NMR (500 MHz, C6D6): δ 8.74 (s, 1H), 8.21 (s,
1H), 7.82 (d, 3J(H,H) = 7.6 Hz, 6H), 7.78 (d, 3J(H,H) = 8.8 Hz, 1H),
7.72 (d, 3J(H,H) = 8.3 Hz, 1H), 7.54 (d, 3J(H,H) = 7.8 Hz, 1H), 7.49 (d,
3J(H,H) = 8.6 Hz, 1H), 7.40 (m, 1H), 7.35 (d, 3J(H,H) = 8.8 Hz, 1H),
7.25 (vt, 3J(H,H) = 7.6, 7.3 Hz, 1H), 7.20 (t, 3J(H,H) = 7.8 Hz, 3H), 7.14
(m, 1H), 7.12−7.08 (t, 3J(H,H) = 7.6 Hz, 6H), 7.05−7.00 (m, 3H), 6.93
General Procedure for the Preparation of Aminodiol
Proligands 8. To a suspension of aminophenol 4 (0.55 mmol) and
aldehyde 5 (0.60 mmol) in toluene (10 mL) was added TsOH·H2O (3.1
mg, 2 mol %), and the mixture was stirred at 100 °C for 2 days. The
solvent was evaporated, and the residue was purified by flash
chromatography on a short silica pad (hexanes/EtOAc 10/1). The
eluate was evaporated, and the residue was immediately subjected to the
reduction as follows. The yellow Schiff base was dissolved in Et2O (15
mL), and LiAlH4 (100 mg, 3.1 mmol) was added in one portion. The
originally yellow solution turned green immediately upon addition of
the hydride. The mixture was stirred at room temperature for an
additional 10 min (TLC), quenched with 2% KOH (10 mL), and
extracted with ethyl acetate (2 × 20 mL). The combined organic extracts
were dried (Na2SO4), and the solvent was evaporated to yield crude
secondary amine 6. Compound 6b was characterized by NMR
spectroscopy; other secondary amines were used further without
characterization. The salane compound 6 was dissolved in THF (10
mL), and formalin (30% solution, 0.36 mL, 4 mmol) and NaBH(OAc)3
(420 mg, 2.0 mmol) were added in one portion at room temperature.
The mixture was stirred for 20 min (monitored by TLC) and then
quenched with 2% KOH (20 mL) and extracted with Et2O (2 × 50 mL).
The combined organic layers were dried (Na2SO4) and passed through a
short alumina plug. Compound 7b was characterized by NMR
spectroscopy, and all other aminals were used further without
characterization. To a stirred eluate containing cyclic aminal
intermediate 7 was added LiAlH4 (40 mg, 1.0 mmol) in one portion
at room temperature. The mixture was stirred for 10 min and then
quenched with 2% KOH (50 mL) and extracted with Et2O (3 × 40 mL).
The combined organic layers were passed through a short alumina plug
and concentrated. The residue was dissolved in benzene (5 mL) and
freeze-dried to yield the proligand 8.
2′-{[2-Hydroxy-5-methyl-3-(methyldiphenylsilyl)benzyl]amino}-3-
(triphenylsilyl)-1,1′-binaphthalen-2-ol (6b). Obtained via the general
procedure from 4a and 5b. White solid, 64% yield. 1H NMR (500 MHz,
C6D6): δ 8.23 (s, 1H), 7.86−7.84 (m, 6H), 7.65 (m, 2H), 7.61−7.57 (m,
3H), 7.49 (d, 3J(H,H) = 9.1 Hz, 1H), 7.39 (d, 3J(H,H) = 7.6 Hz, 1H),
7.27−7.20 (m, 11H), 7.14−7.06 (m, 11H), 7.02−6.98 (m, 2H), 6.75 (s,
1H), 3.82 (vt, 3J(H,H) = 4.7, 3.7 Hz, 1H, NH), 3.64 (dd, 2J(H,H) = 15.7
Hz, 3J(H,H) = 3.7 Hz, 1H, CH2), 3.59 (dd, 2J(H,H) = 15.7 Hz, 3J(H,H)
= 4.7 Hz, 1H, CH2), 2.03 (s, 3H, ArCH3), 0.93 (s, 3H, SiCH3). 13C{1H}
NMR (125 MHz, C6D6): δ 159.9, 156.4 (CO), 145.2, 142.0, 137.18,
137.17, 137.1, 136.9, 135.62, 135.60, 135.31, 135.1, 134.0, 131.0, 130.9,
129.9, 129.7, 129.46, 129.44, 129.1, 128.6, 128.5, 128.08, 128.06, 124.5,
124.3, 124.2, 124.1, 123.8, 122.8, 122.7, 116.2, 113.5, 112.9 (aryl), 48.1
(CH2), 20.6 (ArCH3), −2.6 (SiCH3).
2′-[6-Methyl-8-(methyldiphenylsilyl)-2H-1,3-benzoxazin-3(4H)-
yl]-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (7b). To a stirred solution
of 6b (340 mg, 0.4 mmol) and formalin (0.36 mL, 4 mmol) in THF (10
mL) was added NaBH(OAc)3 (420 mg, 2 mmol) in one portion at room
temperature. The mixture was stirred for 10 min and then quenched
with 2% KOH (10 mL) and extracted with Et2O (2 × 50 mL). The
combined organic layers were passed through a short alumina plug and
evaporated to give 300 mg (96%) of the cyclic aminal 7b as an off-white
solid which quickly oxidizes in air. 1H NMR (400 MHz, C6D6): δ 8.15 (s,
1H), 7.82 (d, 3J(H,H) = 7.0 Hz, 6H), 7.63−7.59 (m, 6H), 7.39−7.35 (m,
2H), 7.30 (d, 3J(H,H) = 8.6 Hz, 1H), 7.22−7.05 (m, 13H), 7.11−7.05
(m, 4H), 6.98−6.92 (m, 4H), 6.23 (s, 1H, aryl-H), 5.07 (s, 1H, OH),
4.60 (d, 2J(H,H) = 10.6 Hz, 1H, OCH2), 4.35 (d, 2J(H,H) = 10.6 Hz,
1H, OCH2), 3.82 (d, 2J(H,H) = 16.8 Hz, 1H, CH2), 3.82 (d, 2J(H,H) =
16.8 Hz, 1H, CH2), 3.76 (d, 2J(H,H) = 16.8 Hz, 1H, CH2), 1.89 (s, 3H,
ArCH3), 0.91 (s, 3H, SiCH3). 13C{1H} NMR (100 MHz, C6D6): δ
157.2, 155.2 (CO), 147.8, 141.3, 137.32, 137.28, 136.9, 136.4, 135.68,
135.67, 135.5, 135.4, 134.1, 131.6, 130.6, 129.9, 129.8, 129.64, 129.58,
129.35, 129.32, 129.29, 128.5, 128.1, 128.0, 127.9, 127.2, 125.7, 125.2,
2
(s, 1H, aryl-H), 4.29 (s, 1H, OH), 3.92 (d, J(H,H) = 13.2 Hz, 1H,
CH2), 3.58 (d, 2J(H,H) = 13.2 Hz, 1H, CH2), 2.31 (s, 3H, CH3), 1.40 (s,
9 H, C(CH3)3), 1.33 (s, 9H, C(CH3)3). 13C{1H} NMR (125 MHz,
C6D6): δ 155.4, 154.5, 151.0, 142.1, 140.4, 136.9, 135.9, 135.6, 135.1,
133.9, 132.8, 130.7, 130.6, 129.6, 129.3, 128.5, 128.3, 128.1, 127.9, 127.5,
126.5, 126.4, 123.9, 123.8, 123.7, 123.3, 121.3, 120.3, 115.9 (aryl), 63.6
(CH2), 40.4 (NCH3), 35.0 (C(CH3)3), 34.3 (C(CH3)3), 32.0
(C(CH3)3), 29.7 (C(CH3)3). Anal. Calcd for C54H53NO2Si: C, 83.57;
H, 6.88; N, 1.80. Found: C, 82.31; H, 7.06; N, 1.68.
2′-{[2-Hydroxy-5-methyl-3-(methyldiphenylsilyl)benzyl]-
methylamino}-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (8b). Pre-
pared from 7b. White solid, 97% yield. 1H NMR (500 MHz, C6D6): δ
3
8.24 (s, 1H), 8.14 (s, 1H), 7.84 (d, J(H,H) = 6.8 Hz, 6H), 7.75 (d,
3J(H,H) = 9.1 Hz, 1H), 7.70 (d, 3J(H,H) = 7.8 Hz, 1H), 7.61−7.56 (m,
2H), 7.48 (d, 3J(H,H) = 6.4 Hz, 2H), 7.44 (m, 3J(H,H) = 8.7 Hz, 1H),
3
7.31−7.28 (m, 2H), 7.24 (t, J(H,H) = 7.6 Hz, 6H), 7.18−7.08 (m,
11H), 7.03−6.93 (m, 3H), 6.73 (s, 1H, aryl-H), 4.26 (s, 1H, OH), 3.87
2
2
(d, J(H,H) = 13.2 Hz, 1H, CH2), 3.61 (d, J(H,H) = 13.2 Hz, 1H,
CH2), 2.24 (s, 3H, NCH3), 2.06 (s, 3H, ArCH3), 0.78 (s, 3H, SiCH3).
13C{1H} NMR (125 MHz, C6D6): δ 160.8, 155.2 (CO), 150.9, 142.1,
137.73, 137.65, 137.63, 136.9, 135.7, 135.5, 135.2, 135.1, 133.8, 132.6,
132.1, 130.7, 130.2, 129.6, 129.4, 129.1, 128.9, 128.5, 128.1, 127.93,
127.89, 127.77, 127.6, 127.5, 127.3, 126.3, 126.1, 123.8, 123.6, 123.4,
122.2, 120.1, 115.8 (aryl), 62.0 (CH2), 40.7 (NCH3), 20.6 (ArCH3),
−2.3 (SiCH3). Anal. Calcd for C60H51NO2Si2: C, 82.43; H, 5.88; N,
1.60. Found: C, 82.06; H, 6.52; N, 1.54.
2′-{[2-Hydroxy-5-methyl-3-(triphenylsilyl)benzyl]methylamino}-
3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (8c). Prepared from 4a and
5c. White solid, 72% yield. 1H NMR (400 MHz, C6D6): δ 8.06 (s, 1H),
7.82 (s, 1H), 7.77 (d, 3J(H,H) = 7.0 Hz, 6H), 7.67 (d, 3J(H,H) = 9.0 Hz,
1H), 7.63 (d, 3J(H,H) = 8.2 Hz, 1H), 7.57 (d, 3J(H,H) = 7.4 Hz, 6H),
3
7.36 (d, J(H,H) = 8.6 Hz, 1H), 7.22−6.93 (m, 23H), 6.74−6.70 (m,
2H, aryl-H), 4.25 (s, 1H, OH), 3.84 (d, 2J(H,H) = 12.9 Hz, 1H, CH2),
3.58 (d, 2J(H,H) = 12.9 Hz, 1H, CH2), 2.15 (s, 3H, NCH3), 1.99 (s, 3 H,
ArCH3). 13C{1H} NMR (100 MHz, C6D6): δ 160.4, 155.0 (CO), 150.8,
142.1, 138.8, 136.9, 136.8, 135.7, 135.3, 134.6, 133.7, 132.8, 132.2, 130.5,
130.0, 129.6, 129.3, 129.2, 128.1, 127.8, 127.5, 126.1, 126.0, 125.7, 124.0,
123.3, 122.8, 121.1, 120.9, 120.8, 115.9 (aryl), 60.9 (CH2), 40.5
(NCH3), 20.6 (ArCH3). Anal. Calcd for C65H53NO2Si2: C, 83.38; H,
5.71; N, 1.50. Found: C, 83.68; H, 5.72; N, 1.54.
2′-{[2-Hydroxy-5-methyl-3-[tris(3,5-dimethylphenyl)silyl]benzyl]-
methyl)amino}-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (8d). Pre-
1
pared from 4a and 5d. White solid, 82% yield. H NMR (400 MHz,
C6D6): δ 8.12 (s, 1H), 7.80 (d, 3J(H,H) = 7.8 Hz, 6H), 7.64 (d, 3J(H,H)
= 8.2 Hz, 1H), 7.63 (d, 3J(H,H) = 9.0 Hz, 1H), 7.59 (m, 1H), 7.57 (s,
6H), 7.39−7.36 (m, 3 H), 7.26 (d, 3J(H,H) = 9.3 Hz, 1H), 7.22−7.16
3
(m, 9 H), 7.09 (d, J(H,H) = 8.6 Hz, 1H), 7.02 (t, 3J(H,H) = 7.7 Hz,
1H), 6.97 (vt, 3J(H,H) = 8.1, 6.9 Hz, 1H), 6.90 (d, 3J(H,H) = 7.7 Hz,
1H), 6.87 (s, 3H), 6.63 (s, 1H, aryl-H), 4.79 (s, 1H, OH), 3.93 (d,
2J(H,H) = 13.7 Hz, 1H, CH2), 3.90 (d, 2J(H,H) = 13.7 Hz, 1H, CH2),
2.43 (s, 3H, NCH3), 2.09 (s, 18H, 6 ArCH3), 1.95 (s, 3H, ArCH3).
13C{1H} NMR (100 MHz, C6D6): δ 160.0, 155.4, 150.6, 141.5, 138.7,
137.0, 136.9, 135.5, 135.4, 135.3, 134.6, 134.1, 133.3, 131.7, 131.5, 130.4,
129.7, 129.6, 129.2, 128.8, 128.5, 128.0, 127.3, 125.58, 125.55, 124.4,
124.2, 123.8, 123.7, 122.7, 122.1, 121.4, 116.9 (aryl), 58.5 (CH2), 40.4
(NCH3), 21.5 (ArCH3), 20.6 (ArCH3).
2′-{[3-(tert-Butyldiphenylsilyl)-2-hydroxy-5-methylbenzyl]-
methylamino}-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (8e). Pre-
1
pared from 4a and 5e. White solid, 85% yield. H NMR (400 MHz,
C6D6): δ 8.13 (br s, 1H), 8.02 (s, 1H), 7.76 (d, 3J(H,H) = 7.1 Hz, 6H),
1402
dx.doi.org/10.1021/om3010614 | Organometallics 2013, 32, 1394−1408

Organometallics
Article
7.71 (d, 3J(H,H) = 9.0 Hz, 1H), 7.65 (d, 3J(H,H) = 8.2 Hz, 1H), 7.61 (d,
3J(H,H) = 6.7 Hz, 2H), 7.52 (d, 3J(H,H) = 7.1 Hz, 2H), 7.33 (d, 3J(H,H)
= 8.6 Hz, 1H), 7.29 (d, 3J(H,H) = 9.0 Hz, 1H), 7.21−6.95 (m, 21H),
6.83 (vt, 3J(H,H) = 6.7, 7.8 Hz, 1 H), 6.70 (s, 1H, aryl-H), 4.19 (s, 1H,
OH), 3.98 (d, 2J(H,H) = 13.3 Hz, 1H, CH2), 3.56 (d, 2J(H,H) = 13.3 Hz,
1H, CH2), 2.29 (s, 3H, CH3), 1.97 (s, 3H, CH3), 1.10 (s, 9H, C(CH3)3).
13C{1H} NMR (100 MHz, C6D6): δ 160.1, 155.1, 150.9, 142.3, 139.9,
136.9, 136.75, 136.72, 136.3, 135.2, 134.8, 133.7, 132.6, 132.3, 130.7,
129.6, 128.9, 128.8, 128.5, 128.1, 127.9, 127.7, 127.5, 127.0, 126.3, 126.0,
124.0, 123.4, 123.2, 121.6, 121.0, 120.5, 115.8 (aryl), 62.1 (CH2), 40.6
(NCH3), 30.3, 20.6, 18.8. Anal. Calcd for C63H57NO2Si2: C, 82.58; H,
6.27; N, 1.53. Found: C, 81.72; H, 6.33; N, 1.43.
1H NMR (500 MHz, C6D6): δ 7.99 (d, 3J(H,H) = 9.0 Hz, 1H), 7.88 (s,
1H), 7.74 (d, 3J(H,H) = 7.8 Hz, 6H), 7.68 (d, 3J(H,H) = 8.2 Hz, 1H),
7.65 (d, 3J(H,H) = 9.3 Hz, 1H), 7.62 (d, 3J(H,H) = 8.1 Hz, 1H), 7.51 (s,
1H), 7.32−7.26 (m, 7H), 7.13−6.79 (m, 20H, aryl-H), 4.48 (d, 2J(H,H)
= 12.2 Hz, 1H, CH2N), 3.60 (d, 2J(H,H) = 12.2 Hz, 1H, CH2N), 3.53 (d,
2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2), 3.25 (s, 4H, free
C6H5NCH2NMe2), 2.98 (d, 2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2),
2.47 (s, 3H, NCH3), 2.06 (s, 12 H, free C6H5CH2NMe2), 1.75 (br s, 3H,
o-C6H4CH2NMe2), 1.44 (s, 9 H, C(CH3)3), 1.41 (s, 9H, C(CH3)3), 1.01
(s, 3H, o-C6H4CH2NMe2). 13C{1H} NMR (100 MHz, C6D6): δ 179.7
1
(d, J(C,Y) = 62 Hz, C−Y), 164.4 (CO), 161.1 (CO), 146.1, 142.9,
142.3, 140.0, 138.3, 138.2, 137.8, 136.8, 136.6, 136.1, 135.7, 132.1, 131.3,
130.9, 129.6, 129.1, 128.9, 128.5, 128.3, 127.6, 127.5, 127.4, 127.2, 127.0,
126.4, 126.3, 126.2, 125.4, 125.0, 124.9, 124.4, 123.,7 121.8, 120.0, 118.2
(aryl), 67.0 (CH2N), 64.5 (free C6H5CH2NMe2), 59.1 (CH2N), 45.4
(free C6H5CH2NMe2), 44.5 (N(CH3)2), 43.2 (N(CH3)2), 38.5
(CH3N), 35.4 (C(CH3)3), 34.3 (C(CH3)3), 32.2 (C(CH3)3), 30.1
(C(CH3)3).
2′-{[2-Hydroxy-5-methyl-3-(triisopropylsilyl)benzyl]-
methylamino}-3-(triphenylsilyl)-1,1′-binaphthalen-2-ol (8f). Pre-
1
pared from 4a and 5f. White solid, 60% yield. H NMR (300 MHz,
C6D6): δ 8.14 (s, 1H), 8.05 (s, 1H), 7.78 (d, 3J(H,H) = 8.6 Hz, 6H), 7.74
3
3
(m, 1H), 7.69 (d, J(H,H) = 7.9 Hz, 1H), 7.48 (d, J(H,H) = 7.9 Hz,
1H), 7.40 (d, 3J(H,H) = 8.5 Hz, 1H), 7.30 (d, 3J(H,H) = 9.1 Hz, 1H),
7.25−7.04 (m, 14H), 6.74 (br s, 1H, aryl-H), 4.18 (s, 1H, OH), 3.90 (d,
2J(H,H) = 13.2 Hz, 1H, CH2), 3.57 (d, 2J(H,H) = 13.2 Hz, 1H, CH2),
(S)-[Lu{NOBIN-TPS/t-Bu}(o-C6H4CH2NMe2)] ((S)-9a-Lu). To a mix-
ture of (S)-8a (23.6 mg, 0.038 mmol) and [Lu(o-C6H4CH2NMe2)3]
(22.0 mg, 0.038 mmol) was added C6D6 (0.55 mL). The mixture was
kept at room temperature for 30 min. 1H and 13C NMR spectra showed
clean formation of (S)-9a-Lu, which was used directly for catalytic
experiments. 1H NMR (500 MHz, C6D6, 60 °C): δ 7.98 (d, 3J(H,H) =
2.27 (s, 3H, CH3), 2.26 (s, 3H, CH3), 1.30 (sept, 3J(H,H) = 6.5 Hz, 3H,
3 CH(CH3)2), 1.09−1.04 (m, 18H, CH(CH3)2). 13C{1H} NMR (75
MHz, C6D6): δ 160.6, 155.2 (CO), 151.0, 142.1, 137.1, 136.9, 135.4,
135.2, 133.8, 132.7, 131.2, 130.7, 130.3, 129.6, 129.4, 128.5, 127.9, 127.5,
127.3, 127.2, 126.4, 126.0, 123.8, 123.7, 123.6, 121.5, 121.0, 120.2, 115.7
(aryl), 62.2 (CH2), 40.7 (NCH3), 20.9 (ArCH3), 19.5 (CH(CH3)2),
19.4 (CH(CH3)2), 12.0 (CH(CH3)2).
3
9.0 Hz, 1H), 7.92 (s, 1H), 7.76 (d, J(H,H) = 7.8 Hz, 6H), 7.66 (d,
3J(H,H) = 9.0 Hz, 1H), 7.62 (d, 3J(H,H) = 8.8 Hz, 1H), 7.55 (d, 4J(H,H)
= 2.2 Hz, 1H), 7.32−7.26 (m, 6H), 7.19−6.90 (m, 20H, aryl-H), 6.86−
6.78 (m, 3H), 6.64 (d, 3J(H,H) = 7.3 Hz, 1H), 6.48 (d, 3J(H,H) = 7.3 Hz,
1H), 4.57 (d, 2J(H,H) = 12.2 Hz, 1H, CH2N), 3.69 (d, 2J(H,H) = 12.2
Hz, 1H, CH2N), 3.62 (d, 2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2),
3.24 (s, 4H, free C6H5NCH2NMe2), 2.88 (d, 2J(H,H) = 13.7 Hz, 1H, o-
C6H4CH2NMe2), 2.44 (s, 3H, NCH3), 2.06 (s, 12 H, free
C6H5CH2NMe2), 1.75 (s, 3H, o-C6H4CH2NMe2), 1.46 (s, 9 H,
C(CH3)3), 1.42 (s, 9H, C(CH3)3), 1.31 (s, 3H, o-C6H4CH2NMe2).
13C{1H} NMR (125 MHz, C6D6): δ 187.5 (C−Lu), 165.0 (CO), 161.5
(CO), 146.2, 143.0, 140.0, 139.7, 138.3, 137.8, 136.8, 136.7, 136.2,
132.1, 130.6, 129.6, 129.1, 128.93, 128.87, 128.5, 128.4, 128.3, 127.9,
127.7, 127.4, 120.1, 118.3 (aryl), 66.2 (CH2N), 64.5 (free
C6H5CH2NMe2), 59.2 (CH2N), 45.4 (free C6H5CH2NMe2), 44.8
(N(CH3)2), 43.6 (N(CH3)2), 38.6 (CH3N), 35.3 (C(CH3)3), 34.2
(C(CH3)3), 32.2 (C(CH3)3), 30.7 (C(CH3)3).
2′-[(3,5-Di-tert-Butyl-2-hydroxybenzyl)methylamino]-3-(methyl-
diphenylsilyl)-1,1′-binaphthalen-2-ol (8g). Prepared from 4b and 5a.
White solid, 71% yield. 1H NMR (500 MHz, C6D6): δ 8.61 (s, 1H), 8.13
(s, 1H), 7.74 (d, 3J(H,H) = 8.6 Hz, 6H), 7.71−7.66 (m, 4H), 7.55 (d,
3J(H,H) = 8.2 Hz, 1H), 7.41 (d, 3J(H,H) = 8.2 Hz, 1H), 7.36 (d, 4J(H,H)
= 2.4 Hz, 1H), 7.31 (d, 3J(H,H) = 8.4 Hz, 1H), 7.20−7.11 (m, 6H, aryl-
H overlapping with C6D5H), 7.05−7.01 (m, 1H), 6.99−6.93 (m, 5H),
4
6.87 (d, J(H,H) = 2.4 Hz, 1H, aryl-H), 4.27 (s, 1H, OH), 3.82 (d,
2J(H,H) = 13.3 Hz, 1H, CH2), 3.63 (d, 2J(H,H) = 13.3 Hz, 1H, CH2),
2.24 (s, 3H, CH3), 1.35 (s, 9 H, C(CH3)3), 1.34 (s, 9H, C(CH3)3), 1.02
(s, 3H, SiCH3). 13C{1H} NMR (100 MHz, C6D6): δ 155.5, 154.4 (CO),
151.0, 140.8, 140.7, 140.4, 137.1, 136.8, 135.9, 135.8, 135.7, 135.5, 135.4,
134.0, 132.7, 130.9, 130.7, 130.4, 129.4, 129.3, 126.5, 125.3, 123.9, 123.7,
123.4, 123.2, 121.4, 121.3, 120.3, 115.3 (aryl), 63.3 (CH2), 40.4
(NCH3), 35.0 (C(CH3)3), 34.3 (C(CH3)3), 32.1 (C(CH3)3), 29.8
(C(CH3)3), −2.9 (SiCH3).
(S)-[Y{NOBIN-TPS/SiPh2Me}(o-C6H4CH2NMe2)] ((S)-9b-Y). To a
mixture of (S)-8b (29.0 mg, 0.033 mmol) and [Y(o-C6H4CH2NMe2)3]
(16.3 mg, 0.033 mmol) was added C6D6 (0.55 mL). The mixture was
kept at room temperature for 30 min. 1H and 13C NMR spectra showed
clean formation of (S)-9b-Y, which was used directly for catalytic
experiments. 1H NMR (500 MHz, C6D6, 60 °C): δ 7.94 (d, 3J(H,H) =
9.0 Hz, 1H), 7.76 (d, 3J(H,H) = 7.8 Hz, 6H), 7.53−6.57 (m, 40H), 6.54
2′-{[2-Hydroxy-5-methyl-3-(methyldiphenylsilyl)benzyl]-
methylamino}-3-(methyldiphenylsilyl)-1,1′-binaphthalen-2-ol (8h).
1
Prepared from 4b and 5b. White solid, 93% yield. H NMR (500
MHz, C6D6): δ 8.17 (s, 1H), 8.03 (s, 1H), 7.75 (d, 3J(H,H) = 8.6 Hz,
1H), 7.68 (m, 5H), 7.60 (m, 1H), 7.49 (d, 3J(H,H) = 7.1 Hz, 1H), 7.39
(d, 3J(H,H) = 7.8 Hz, 1H), 7.31 (d, 3J(H,H) = 8.6 Hz, 1H), 7.24−7.08
(m, 15H), 6.98 (m, 4H), 6.70 (s, 1H, aryl-H), 4.31 (s, 1H, OH), 3.82 (d,
2J(H,H) = 13.2 Hz, 1H, CH2), 3.67 (d, 2J(H,H) = 13.2 Hz, 1H, CH2),
2.23 (s, 3H, NCH3), 2.04 (s, 3H, ArCH3), 1.00 (s, 3H, SiCH3), 0.85 (s,
3H, SiCH3). 13C{1H} NMR (125 MHz, C6D6): δ 160.8, 155.4 (CO),
150.9, 140.7, 137.74, 137.66, 137.2, 136.8, 135.8, 135.7, 135.6, 135.0,
133.9, 132.5, 132.2, 130.8, 130.0, 129.44, 129.38, 128.9, 128.5, 127.1,
126.3, 126.2, 124.9, 123.7, 122.1, 121.2, 120.1, 115.2 (aryl), 61.8 (CH2),
40.8 (NCH3), 20.5 (ArCH3), −2.3 (SiCH3), −2.7 (SiCH3).
2
(m, 2H, aryl-H), 4.47 (d, J(H,H) = 12.2 Hz, 1H, CH2N), 3.78 (d,
2J(H,H) = 12.2 Hz, 1H, CH2N), 3.21 (s, 4H, free C6H5NCH2NMe2),
2.70 (d, 2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2), 2.47 (s, 3H,
NCH3), 2.32 (d, 2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2), 2.03 (s, 12
H, free C6H5CH2NMe2), 1.22 (s, 3H, o-C6H4CH2NMe2), 1.04 (s, 3H, o-
C6H4CH2NMe2), 0.78 (s, 3H, SiCH3). 13C{1H} NMR (100 MHz,
C6D6): δ 179.4 (d, 1J(C,Y) = 61 Hz, C−Y), 168.4 (CO), 164.6 (CO),
146.5, 143.0, 140.4, 140.0, 139.0, 138.1, 137.72, 137.67, 137.03, 136.98,
136.9, 136.8, 136.7, 136.1, 136.0, 135.6, 135.4, 135.3, 132.0, 131.0,
129.81, 129.76, 129.3, 129.1, 129.04, 129.01, 128.54, 128.50, 128.45,
128.4, 128.1, 127.6, 127.4, 127.2, 126.5, 126.4, 126.0, 125.3, 125.2, 124.8,
124.6, 122.7, 121.8, 121.31, 120.0, 118.2 (aryl), 65.9 (CH2N), 64.5 (free
C6H5CH2NMe2), 58.7 (CH2N), 45.4 (free C6H5CH2NMe2), 44.0
(N(CH3)2), 42.6 (N(CH3)2), 38.7 (NCH3), 20.5 (ArCH3), −1.0
(SiCH3).
General Procedure for the NMR-Scale Preparation of 9-Ln. To
a mixture of diol proligand 8 (0.05 mmol) and the rare-earth-metal
precursor (0.05 mmol) was added C6D6 (490 mg, 500 μL). The mixture
was shaken vigorously and then left for 5 min at room temperature or
slightly elevated temperature. Clean quantitative conversion to the
diolate complex 9-Ln was confirmed by NMR spectroscopy. Aliquots of
the resulting complex solution were used directly for the catalytic
experiments.
(S)-[Y{NOBIN-TPS/TPS}(o-C6H4CH2NMe2)] ((S)-9c-Y). To a mixture
of (S)-8c (23.4 mg, 0.025 mmol) and [Y(o-C6H4CH2NMe2)3] (12.3
mg, 0.025 mmol) was added C6D6 (0.55 mL). The mixture was kept at
room temperature for 30 min. 1H and 13C NMR spectra showed clean
formation of (S)-9c-Y, which was used directly for catalytic experiments.
1H NMR (500 MHz, C6D6, 65 °C): δ 7.98 (s, 1H), 7.86 (d, 3J(H,H) =
(S)-[Y{NOBIN-TPS/t-Bu}(o-C6H4CH2NMe2)] ((S)-9a-Y). To a mixture
of (S)-8a (28.4 mg, 0.036 mmol) and [Y(o-C6H4CH2NMe2)3] (18.0
mg, 0.036 mmol) was added C6D6 (0.55 mL). The mixture was kept at
1
room temperature for 2 h. H and 13C NMR spectra showed clean
formation of (S)-9a-Y, which was used directly for catalytic experiments.
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3
9.3 Hz, 1H), 7.72 (d, J(H,H) = 7.8 Hz, 6H), 7.69 (m, 2H), 7.60 (d
3J(H,H) = 7.8 Hz, 6H), 7.58 (m, 2H), 7.37 (d, 3J(H,H) = 8.8 Hz, 2H),
NMR spectra showed clean formation of (R)-9d-Lu, which was used
directly for catalytic experiments. 1H NMR (500 MHz, C6D6): δ 8.07 (s,
1H), 8.06 (m, 1H), 7.76 (d, 3J(H,H) = 9.1 Hz, 1H), 7.71 (d, 3J(H,H) =
7.3 Hz, 6H), 7.62 (d, 3J(H,H) = 8.3 Hz, 1H), 7.57 (s, 6H), 7.44 (m, 1H),
7.32 (d 3J(H,H) = 8.1 Hz, 6H), 7.21−7.01 (m, 15H including 10H from
C6H5CHNMe2 and 2H from C6D5H), 6.90−6.75 (m, 14H), 6.64 (d,
3J(H,H) = 8.3 Hz, 1H, aryl-H), 5.20 (br s, 1H, CH2N), 3.93 (br s, 1H,
CH2N), 3.55 (br s, 1H, o-C6H4CH2NMe2), 3.22 (s, 4H, free
3
7.27 (d, J(H,H) = 7.1 Hz, 12H), 7.20 (m, 1H), 7.18−6.85 (m, 27H,
including 10 H from free C6H5CH2NMe2 and 10H from C6D5H), 6.77
(m, 2H), 6.71 (m, 1H), 6.86−6.78 (m, 3H), 6.57 (d, 3J(H,H) = 8.3 Hz,
1H), 6.47 (d, 3J(H,H) = 7.3 Hz, 1H, aryl), 4.42 (d, 2J(H,H) = 12.7 Hz,
1H, CH2N), 4.26 (d, 2J(H,H) = 12.7 Hz, 1H, CH2N), 3.24 (s, 4H, free
C6H5NCH2NMe2), 2.75 (d, 2J(H,H) = 13.9 Hz, 1H, o-C6H4CH2NMe2),
2.66 (s, 3H, NCH3), 2.49 (d, 2J(H,H) = 13.7 Hz, 1H, o-
C6H4CH2NMe2), 2.07 (3H, CH3C), 2.06 (s, 12 H, free
C6H5CH2NMe2), 0.86 (br s, 6H, o-C6H4CH2NMe2). 13C{1H} NMR
2
C6H5NCH2NMe2), 2.88 (s, 3H, NCH3), 2.19 (d, J(H,H) = 14.7 Hz,
1H, o-C6H4CH2NMe2), 2.08 (3H, ArCH3), 2.04 (s, 12 H, free
C6H5CH2NMe2), 1.97 (s, 18H, 6 ArCH3), 1.23 (s, 3H, o-
C6H4CH2NMe2), 0.35 (s, 3H, o-C6H4CH2NMe2). 13C{1H} NMR
(125 MHz, C6D6): δ 187.2 (C−Lu), 168.5 (CO), 164.5 (CO), 147.1,
143.1, 142.9, 141.5, 140.3, 140.0, 137.9, 137.2, 136.8, 136.5, 135.9, 135.6,
134.8, 132.4, 131.5, 130.2, 129.4, 129.1, 128.8, 128.54, 128.47, 128.3,
127.7, 127.6, 127.2, 126.9, 125.7, 124.9, 122.0, 120.0 (aryl), 65.8
(CH2N), 64.5 (free C6H5CH2NMe2), 58.1 (CH2N), 45.4 (free
C6H5CH2NMe2), 42.8 (N(CH3)2), 42.5 (N(CH3)2), 40.3 (NCH3),
21.4 (6 ArCH3), 20.6 (ArCH3).
1
(125 MHz, C6D6): δ 179.9 (d, J(C,Y) = 60 Hz, C−Y), 168.3 (CO),
164.9 (CO), 146.6, 143.0, 141.0, 140.0, 138.4, 137.6, 136.93, 136.87,
136.81, 136.75, 135.6, 135.4, 131.8, 130.8, 130.7, 129.7, 129.3, 129.1,
128.5, 128.3, 128.1, 127.9, 127.5, 127.4, 127.2, 126.7, 126.5, 125.9, 125.5,
125.2, 125.7, 124.6, 123.7, 121.9, 120.4, 120.3, 118.1 (aryl), 66.5
(CH2N), 64.5 (free C6H5CH2NMe2), 58.9 (CH2N), 45.4 (free
C6H5CH2NMe2), 43.0 (N(CH3)2), 42.9 (N(CH3)2), 39.4 (CH3N),
20.6 (CH3C).
(S)-[Y{NOBIN-TPS/TBDPS}(o-C6H4CH2NMe2)] ((S)-9e-Y). To a mix-
ture of (S)-8e (27.5 mg, 0.030 mmol) and [Y(o-C6H4CH2NMe2)3]
(14.8 mg, 0.030 mmol) was added C6D6 (0.55 mL). The mixture was
(S)-[Lu{NOBIN-TPS/TPS}(o-C6H4CH2NMe2)] ((S)-9c-Lu). To a mix-
ture of (S)-8c (23.4 mg, 0.025 mmol) and [Lu(o-C6H4CH2NMe2)3]
(14.3 mg, 0.025 mmol) was added C6D6 (0.55 mL). The mixture was
kept at room temperature for 30 min. 1H and 13C NMR spectra showed
clean formation of (S)-9c-Lu, which was used directly for catalytic
experiments. 1H NMR (300 MHz, C6D6,): δ 8.04 (s, 1H), 7.92−7.82 (br
m, 2H), 7.74 (d, 3J(H,H) = 8.0 Hz, 6H), 7.67 (br s, 1H) 7.64−7.58 (m,
7H), 7.41 (d, 3J(H,H) = 6.8 Hz, 1H), 7.32−7.25 (m, 5H), 7.18−7.03 (m,
15H), 6.96−6.91 (m, 12H), 6.88−6.82 (m, 2H), 6.80−6.76 (m, 2H),
6.61 (d, 3J(H,H) =7.9 Hz, 2H), 6.48−6.46 (m, 2H, aryl-H), 4.48 (br s,
1H, CH2), 4.22 (br s, 1H, CH2), 3.23 (s, 4H, free C6H5CH2NMe2), 2.95
(br s, 1H, o-C6H4CH2NMe2), 2.72 (s, 3H, NCH3), 2.38 (d, 2J(H,H) =
13.2 Hz, 1H, o-C6H4CH2NMe2), 2.07 (s, 3H, ArCH3), 2.02 (s, 12H, free
C6H5CH2NMe2), 1.00 (s, 3H, o-C6H4CH2NMe2), 0.55 (s, 3H, o-
C6H4CH2NMe2). 13C{1H} NMR (125 MHz, C6D6): δ 187.5 (C−Lu),
167.4, 165.2, 147.2, 147.0, 143.2, 142.5, 141.0, 139.9, 139.8, 139.3,
137.81, 136.76, 136.5, 132.0, 129.5, 129.2, 129.0, 128.9, 128.3, 127.3,
127.0, 127.3, 126.8, 126.1, 125.6, 125.3, 125.1, 124.9, 124.7, 122.8, 120.9,
120.2, 118.0 (aryl), 65.4 (CH2N), 64.5 (free C6H5CH2NMe2), 46.1
(N(CH3)2), 45.3 (free C6H5CH2NMe2), 43.0 (N(CH3)2), 20.4
(ArCH3).
1
kept at 60 °C for 1 h. The H and 13C NMR spectra showed clean
formation of (S)-9e-Y, which was used directly for catalytic experiments.
1H NMR (400 MHz, C6D6, 70 °C): δ 7.95 (s, 1H), 7.76−7.71 (m, 7H),
7.61 (d, 3J(H,H) = 7.0 Hz, 2H), 7.58 (d, 4J(H,H) = 2.4 Hz, 1H), 7.52 (m,
3H), 7.47 (d, 3J(H,H) = 9.4 Hz, 1H), 7.40 (d, 3J(H,H) = 8.6 Hz, 1H),
7.36 (d, 3J(H,H) = 7.4 Hz, 1H), 7.27 (d, 3J(H,H) = 7.4 Hz, 4H), 7.15−
6.83 (m, 34H, including 10H from free PhCH2NMe2), 6.82 (d, 4J(H,H)
= 2.1 Hz, 1H), 6.57 (d, 3J(H,H) = 8.2 Hz, 1H), 6.43 (d, 3J(H,H) = 7.4
2
Hz, 1H, aryl-H), 4.34 (d, J(H,H) = 13.3 Hz, 1H, ArCH2N), 4.19 (d,
2J(H,H) = 13.3 Hz, 1H, ArCH2N), 3.24 (s, 4H, free C6H5NCH2NMe2),
2.56 (s, 3H, ArCH2NMe), 2.55 (d, 2J(H,H) = 14.1 Hz, 1H, o-
C6H4CH2NMe2), 2.48 (d, 2J(H,H) = 14.1 Hz, 1H, o-C6H4CH2NMe2),
2.20 (s, 3H, ArCH3), 2.06 (s, 12 H, free C6H5CH2NMe2), 1.10 (s, 9H,
C(CH3)3), 0.94 (br s, 6H, o-C6H4CH2NMe2). 13C{1H} NMR (125
MHz, C6D6): δ 180.3 (d, 1J(C,Y) = 59 Hz, C−Y), 168.0, 166.1, 146.3,
143.0, 140.2, 140.0, 138.9, 137.3, 137.2, 136.85, 136.81, 136.79, 136.3,
134.9, 131.2, 131.1, 129.7, 129.1, 129.0, 128.6, 128.53, 128.45, 128.4,
128.29, 128.26, 127.9, 127.4, 127.2, 126.9, 126.3, 125.7, 124.8, 124.7,
124.4, 124.3, 121.8, 120.7, 120.5, 118.6 (aryl), 66.5 (o-C6H4CH2NMe2),
64.5 (free C6H5CH2NMe2), 58.6 (NCH3), 45.4 (free C6H5CH2NMe2),
43.5 (o-C6H4CH2NMe2), 43.1 (o-C6H4CH2NMe2), 38.9 (NCH3), 29.8
(C(CH3)3), 20.7 (ArCH3), 19.3 (C(CH3)3).
(R)-[Y{NOBIN-TPS/Si(Xylyl)3}(o-C6H4CH2NMe2)] ((R)-9d-Y). To a
mixture of (R)-8d (30.8 mg, 0.030 mmol) and [Y(o-C6H4CH2NMe2)3]
(14.8 mg, 0.030 mmol) was added C6D6 (0.55 mL). The mixture was
kept at 60 °C for 3 h. 1H and 13C NMR spectra showed clean formation
of (R)-9d-Y, which was used directly for catalytic experiments. 1H NMR
(400 MHz, C6D6): δ 8.03 (s, 1H), 8.01 (d, 3J(H,H) = 9.0 Hz, 1H), 7.77
(S)-[Lu{NOBIN-TPS/TBDPS}(o-C6H4CH2NMe2)] ((S)-9e-Lu). To a
mixture of (S)-8e (27.5 mg, 0.030 mmol) and [Lu(o-C6H4CH2NMe2)3]
(17.8 mg, 0.030 mmol) was added C6D6 (0.55 mL). The mixture was
kept at 60 °C for 30 min. 1H NMR (500 MHz, C6D6): δ 8.00 (s, 1H),
7.75 (d, 3J(H,H) = 9.3 Hz, 6H), 7.67−7.64 (m, 3H), 7.60 (d, 3J(H,H) =
9.0 Hz, 1H), 7.53−7.40 (m, 4H), 7.31−7.25 (m, 5H), 7.17−6.99 (m,
24H, including 10H from free PhCH2NMe2), 6.83−6.76 (m, 5H), 6.56
(d, 3J(H,H) = 7.3 Hz, 1H), 6.43 (br s, 1H), 4.3 (br s 2H, ArCH2N), 3.22
(s, 4H, free C6H5NCH2NMe2), 2.64−2.56 (m, 4H, ArCH2NMe and o-
C6H4CH2NMe2), 2.50 (d, 2J(H,H) = 13.5 Hz, 1H, o-C6H4CH2NMe2),
2.22 (s, 3H, ArCH3), 2.05 (s, 12 H, free C6H5CH2NMe2), 1.09 (s, 9H,
C(CH3)3), 1.05 (s, 3H, o-C6H4CH2NMe2), 0.78 (s, 3H, o-
C6H4CH2NMe2). 13C{1H} NMR (125 MHz, C6D6): δ 187.6 (C−Lu),
168.2, 165.4, 146.8, 143.3, 140.3, 140.0, 139.7, 137.9, 137.2, 137.0, 136.8,
136.3, 131.9, 129.7, 129.1, 129.0, 128.9, 128.7, 128.53, 128.46, 128.3,
127.6, 127.39, 127.36, 127.2, 126.6, 126.0, 125.7, 125.1, 125.0, 124.8,
121.9, 121.0, 120.4, 118.3 (aryl), 68.2 (CH2N), 65.5 (o-
C6H4CH2NMe2), 64.5 (free C6H5CH2NMe2), 45.4 (free
C6H5CH2NMe2), 43.9 (o-C6H4CH2NMe2), 43.3 (o-C6H4CH2NMe2),
29.8(C(CH3)3), 20.7 (ArCH3), 19.3 (C(CH3)3).
3
3
(d, J(H,H) = 9.3 Hz, 1H), 7.69 (d, J(H,H) = 8.0 Hz, 6H), 7.65 (d,
3J(H,H) = 8.3 Hz, 1H), 7.55 (s, 6H), 7.53 (m, 1H), 7.39 (br s, 1H), 7.35
(d 3J(H,H) = 7.8 Hz, 1H), 7.31 (d 3J(H,H) = 7.8 Hz, 3H), 7.19−7.01
(m, 14H, including 10H from C6H5CHNMe2 and 1H from C6D5H),
6.90−6.75 (m, 13H), 6.72 (d, 3J(H,H) = 7.6 Hz, 1H), 6.67 (d, 3J(H,H) =
8.3 Hz, 1H, aryl-H), 5.16 (d, 2J(H,H) = 13.0 Hz, 1H, CH2N), 4.08 (d,
2J(H,H) = 13.0 Hz, 1H, CH2N), 3.37 (d, J(H,H) = 13.7 Hz, 1H, o-
2
C6H4CH2NMe2), 3.23 (s, 4H, free C6H5NCH2NMe2), 2.84 (s, 3H,
NCH3), 2.29 (d, 2J(H,H) = 13.7 Hz, 1H, o-C6H4CH2NMe2), 2.08 (3H,
ArCH3), 2.06 (s, 12 H, free C6H5CH2NMe2), 1.97 (s, 18H, 6 ArCH3),
1.15 (s, 3H, o-C6H4CH2NMe2), 0.45 (s, 3H, o-C6H4CH2NMe2).
13C{1H} NMR (125 MHz, C6D6): δ 179.5 (d, J(C,Y) = 61 Hz, C−
1
Y), 168.1 (CO), 164.0 (CO), 146.9, 143.3, 143.0, 141.4, 140.0, 139.0,
138.0, 137.3, 137.2, 136.7, 136.6, 135.7, 135.6, 134.8, 132.4, 131.4, 130.4,
129.4, 129.1, 128.9, 128.53, 128.46, 128.3, 128.2, 127.9, 127.2, 126.7,
126.4, 126.3, 125.7, 125.4, 125.3, 124.8, 123.6, 122.0, 121.4, 120.0, 117.1
(aryl), 66.8 (CH2N), 64.5 (free C6H5CH2NMe2), 58.4 (CH2N), 45.4
(free C6H5CH2NMe2), 42.7 (N(CH3)2), 42.5 (N(CH3)2), 40.2
(NCH3), 21.4 (6 ArCH3), 20.6 (ArCH3).
(S)-[Y{NOBIN-TPS/TIPS}(o-C6H4CH2NMe2)] ((S)-9f-Y). To a mixture
of (S)-8f (19.3 mg, 0.023 mmol) and [Y(o-C6H4CH2NMe2)3] (11.3 mg,
0.023 mmol) was added C6D6 (0.52 mL). The mixture was kept at room
(R)-[Lu{NOBIN-TPS/Si(Xylyl)3}(o-C6H4CH2NMe2)] ((R)-9d-Lu). To a
mixture of (R)-8d (30.8 mg, 0.030 mmol) and [Lu(o-
C6H4CH2NMe2)3] (16.0 mg, 0.030 mmol) was added C6D6 (0.55
1
temperature for 10 min. The H and 13C NMR spectra showed clean
formation of (S)-9f-Y, which was used directly for catalytic experiments.
mL). The mixture was kept at room temperature for 1 h. H and 13C
1H NMR (500 MHz, C6D6, 70 °C): δ 7.95 (s, 1H), 7.91 (d, 3J(H,H) =
1
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9.1 Hz, 2H), 7.75 (d, 3J(H,H) = 7.0 Hz, 6H), 7.56 (d, 3J(H,H) = 7.8 Hz,
1H), 7.53 (d, 3J(H,H) = 8.6 Hz, 1H), 7.38 (d, 3J(H,H) = 7.8 Hz, 1H),
7.32−7.25 (m, 5H), 7.17−6.86 (m, 23H, including 10H from free
PhCH2NMe2), 6.67 (m, 2H), 6.57 (d, 3J(H,H) = 7.3 Hz, 1H, aryl-H),
4.35 (d, 2J(H,H) = 12.7 Hz, 1H, ArCH2N), 3.99 (d, 2J(H,H) = 12.7 Hz,
1H, ArCH2N), 3.51 (d, 2J(H,H) = 13.9 Hz, 1H, o-C6H4CH2NMe2), 3.25
(S)-[Y{NOBIN-SiPh2Me/SiPh2Me}(o-C6H4CH2NMe2)] ((S)-9h-Y). To a
mixture of (S)-8h (38.9 mg, 0.048 mmol) and [Y(o-C6H4CH2NMe2)3]
(23.7 mg, 0.048 mmol) was added C6D6 (0.55 mL). The mixture was
1
kept at 50 °C for 40 min. H and 13C NMR spectra showed clean
formation of (S)-9h-Y, which was used directly for catalytic experiments.
1H NMR (500 MHz, C6D6, 65 °C): δ 8.03 (d, 3J(H,H) = 9.0 Hz, 1H),
7.93 (s, 1H), 7.14−7.70 (m, 6H), 7.65 (m, 4H), 7.58 (d, 3J(H,H) = 6.6
Hz, 1H), 7.51 (m, 1H), 7.42−7.38 (m, 3H), 7.31−6.99 (m, 30H,
including 10H from free PhCH2NMe2), 6.88 (m, 2H), 6.83 (d, 4J(H,H)
= 2.2 Hz, 1H), 6.62 (d, 3J(H,H) = 7.3 Hz, 1H), 6.47 (m, 1H, aryl-H),
4.62 (d, 2J(H,H) = 12.7 Hz, 1H, CH2N), 3.87 (d, 2J(H,H) = 12.7 Hz,
2
(s, 4H, free C6H5NCH2NMe2), 2.87 (d, J(H,H) = 13.9 Hz, 1H, o-
C6H4CH2NMe2), 2.50 (s, 3H, ArCH2NMe), 2.23 (s, 3H, ArCH3), 2.06
(s, 12 H, free C6H5CH2NMe2), 1.53 (br s, 3H, o-C6H4CH2NMe2), 1.53
3
(br s, 3H, o-C6H4CH2NMe2), 6.57 (sept, J(H,H) = 7.6 Hz, 3H, 3
3
CH(CH3)2), 1.10 (d, J(H,H) = 7.6 Hz, 9H, 3 CH(CH3)2), 1.05 (d,
2
3J(H,H) = 7.6 Hz, 9H, 3 CH(CH3)2). 13C{1H} NMR (100 MHz, C6D6):
δ 180.0 (d, 1J(C,Y) = 58 Hz, C−Y), 167.7, 166.4, 146.0, 143.0, 140.0,
139.1, 138.2, 136.8, 136.7, 134.1, 131.9, 129.6, 129.14, 129.10, 128.54,
128.45, 127.4, 127.2, 126.9, 126.4, 126.3, 126.0, 124.9, 124.6, 124.4,
124.2, 123.8, 122.0, 121.8, 120.6, 118.4 (aryl), 67.4 (o-C6H4CH2NMe2),
64.5 (free C6H5CH2NMe2), 58.0 (CH2N), 45.4 (free C6H5CH2NMe2),
44.0 (o-C6H4CH2NMe2), 42.9 (o-C6H4CH2NMe2), 38.2 (NCH3), 20.8
(ArCH3), 19.7 (CH(CH3)2), 13.1 (CH(CH3)2).
1H, CH2N), 3.29 (s, 4H, free C6H5NCH2NMe2), 3.11 (d, J(H,H) =
2
13.9 Hz, 1H, o-C6H4CH2NMe2), 2.52 (d, J(H,H) = 13.9 Hz, 1H, o-
C6H4CH2NMe2), 2.35 (s, 3H, NCH3), 2.10 (s, 12 H, free
C6H5CH2NMe2), 2.08 (s, 3H, o-C6H4CH2NMe2), 1.55 (s, 3H, o-
C6H4CH2NMe2), 1.09 (s, 3H, SiCH3), 1.07 (s, 3H, SiCH3). 13C{1H}
1
NMR (125 MHz, C6D6): δ 179.4 (d, J(C,Y) = 61 Hz, C−Y), 168.2
(CO), 164.4 (CO), 146.5, 141.7, 141.6, 140.2, 140.0, 138.8, 138.6,
138.2, 137.8, 137.4, 137.3, 136.1, 136.0, 135.9, 135.7, 135.6, 135.3, 135.2,
132.1, 131.0, 129.8, 129.6, 129.3, 129.2, 129.1, 128.9, 128.5, 128.3, 127.7,
127.3, 127.2, 125.5, 125.4, 124.8, 124.7, 122.6, 121.9, 121.7, 120.1, 117.1
(aryl), 66.3 (CH2N), 64.5 (free C6H5CH2NMe2), 57.9 (CH2N), 45.4
(free C6H5CH2NMe2), 42.4 (N(CH3)2), 39.0 (NCH3), 20.5 (ArCH3),
−0.8 (SiCH3), −2.1 (SiCH3).
(S)-[Lu{NOBIN-TPS/TIPS}(o-C6H4CH2NMe2)] ((S)-9f-Lu). To a mix-
ture of (S)-8f (19.4 mg, 0.023 mmol) and [Lu(o-C6H4CH2NMe2)3]
(13.6 mg, 0.023 mmol) was added C6D6 (0.52 mL). The mixture was
1
kept at room temperature for 30 min. The H and 13C NMR spectra
showed clean formation of (S)-9f-Lu, which was used directly for
1
Typical Procedure for Intermolecular Hydroamination Re-
actions.10b In the glovebox, a screw-cap NMR tube was charged with
an appropriate amine (0.2 mmol), alkene (3 mmol), and a solution of
the catalyst (0.1 M in C6D6, 0.1 mL, 10.0 μmol, 5 mol %). The tube was
then sealed, removed from the glovebox, and placed into the
thermostated oil bath. The progress of the reaction was monitored by
1H NMR spectroscopy. After completion of the reaction, the mixture
catalytic experiments. H NMR (400 MHz, C6D6, 70 °C): δ 7.95 (s,
1H), 7.91 (d, 3J(H,H) = 9.1 Hz, 2H), 7.75 (d, 3J(H,H) = 7.0 Hz, 6H),
7.56 (d, 3J(H,H) = 7.8 Hz, 1H), 7.53 (d, 3J(H,H) = 8.6 Hz, 1H), 7.38 (d,
3J(H,H) = 7.8 Hz, 1H), 7.32−7.25 (m, 5H), 7.17−6.86 (m, 23H,
including 10H from free PhCH2NMe2), 6.67 (m, 2H), 6.57 (d, 3J(H,H)
= 7.3 Hz, 1H, aryl-H), 4.35 (d, 2J(H,H) = 12.7 Hz, 1H, ArCH2N), 3.99
(d, 2J(H,H) = 12.7 Hz, 1H, ArCH2N), 3.51 (d, 2J(H,H) = 13.9 Hz, 1H,
o-C6H4CH2NMe2), 3.24 (s, 4H, free C6H5NCH2NMe2), 2.87 (d,
2J(H,H) = 13.9 Hz, 1H, o-C6H4CH2NMe2), 2.50 (s, 3H, ArCH2NMe),
2.23 (s, 3H, ArCH3), 2.05 (s, 12 H, free C6H5CH2NMe2), 1.53 (br s, 3H,
o-C6H4CH2NMe2), 1.53 (br s, 3H, o-C6H4CH2NMe2), 6.57 (sept,
3J(H,H) = 7.6 Hz, 3H, 3 CH(CH3)2), 1.10 (d, 3J(H,H) = 7.6 Hz, 9H, 3
was concentrated in vacuo and purified by column chromatography on a
3 cm height pad of silica or alumina.
(R)-N-Benzylheptan-2-amine (17a).31 Prepared from 1-heptene and
benzylamine according to Table 4, entry 1. Purified by column
chromatography on alumina (hexanes/EtOAc 100/0.6). Yield 62%;
colorless oil, 36% ee. 1H NMR (400 MHz, CDCl3): δ 7.33−7.30 (m, 4H,
3
CH(CH3)2), 1.05 (d, J(H,H) = 7.6 Hz, 9H, 3 CH(CH3)2). 13C{1H}
2
aryl-H), 7.25−7.21 (m, 1H, aryl-H), 3.82 (d, J(H,H) = 13.0 Hz, 1H,
NMR (100 MHz, C6D6): δ 187.5 (C−Lu), 168.4, 165.7, 146.3, 143.1,
140.0, 139.8, 138.6, 137.7, 136.83, 136.77, 136.0, 133.9, 131.8, 130.7,
129.6, 129.1, 128.9, 128.5, 127.94, 127.88, 127.6, 127.41, 127.4, 127.2,
126.3, 126.2, 126.1, 125.28, 125.25, 124.93, 124.86, 122.3, 121.9, 120.1
(aryl), 66.1 (o-C6H4CH2NMe2), 64.5 (free C6H5CH2NMe2), 58.5
(CH2N), 45.4 (free C6H5CH2NMe2), 43.8 (o-C6H4CH2NMe2), 43.4 (o-
C6H4CH2NMe2), 38.6 (NCH3), 20.8 (ArCH3), 19.6 (CH(CH3)2), 19.5
(CH(CH3)2), 13.1 (CH(CH3)2).
PhCH2NH), 3.73 (d, 2J(H,H) = 13.0 Hz, 1H, PhCH2NH), 2.68 (sext,
3J(H,H) = 6.2 Hz, 1H, CHNH), 1.50−1.41 (m, 1H, CH2) 1.34−1.23
(m, 8H, CH2 and NH), 1.07 (d, 3J(H,H) = 6.2 Hz, 3H, CH3CHNH),
3
0.89 (t, J(H,H) = 6.9 Hz, 3H; CH3CH2). 13C{1H} NMR (100 MHz,
CDCl3): δ 140.9 (Cipso), 128.4, 128.1, 126.8 (aryl), 52.5 (CH(CH3)-
NH), 51.4 (CH2NH), 37.1 (CH2), 32.1 (CH2), 25.7 (CH2), 22.7
(CH2), 20.3 (CH3CHNH), 14.1 (CH3CH2).
(R)-N-Benzyl-4-phenylbutan-2-amine (17b).31 Prepared from 4-
phenyl-1-butene and benzylamine according to Table 4, entry 8. Purified
by column chromatography on silica (CH2Cl2/7 M NH3 in MeOH 100/
(S)-[Y{NOBIN-SiPh2Me/t-Bu}(o-C6H4CH2NMe2)] ((S)-9g-Y). To a
mixture of (S)-8g (26.5 mg, 0.037 mmol) and [Y(o-C6H4CH2NMe2)3]
(18.2 mg, 0.037 mmol) was added C6D6 (0.55 mL). The mixture was
1
1). Yield 52%; colorless oil, 40% ee. H NMR (500 MHz, CDCl3,): δ
1
kept at room temperature for 3 h. H and 13C NMR spectra showed
7.34−7.22 (m, 7H), 7.19−7.16 (m, 3H, aryl-H), 3.82 (d, 2J(H,H) = 13.0
Hz, 1H, PhCH2NH), 3.73 (d, 2J(H,H) = 12.9 Hz, 1H, PhCH2NH), 2.69
(sext, 3J(H,H) = 6.3 Hz, 1H, CHNH), 2.70−2.61 (m, 2H), 1.85−1.78
(m, 1H), 1.71−1.64 (m, 1H), 1.49 (br s, 1H, NH), 1.14 (d, 3J(H,H) =
6.4 Hz, 3H, CH3CHNH). 13C{1H} NMR (125 MHz, CDCl3): δ 142.5
(Cquart), 140.8 (Cquart), 128.35, 128.32, 128.30. 128.1, 126.8, 125.7
(aryl), 52.0 (CH(CH3)NH), 51.3 (CH2NH), 38.7 (CH2), 32.3 (CH2),
20.4 (CH3).
clean formation of (S)-9g-Y, which was used directly for catalytic
experiments. 1H NMR (500 MHz, C6D6, 65 °C): δ 8.03 (d, 3J(H,H) =
9.1 Hz, 1H), 7.87 (s, 1H), 7.69−7.60 (m, 6H), 7.53 (d, 4J(H,H) = 2.4
Hz, 1H), 7.43 (d, 3J(H,H) = 8.6 Hz, 1H), 7.34−6.98 (m, 26H, including
10H from free PhCH2NMe2), 6.91 (d, 4J(H,H) = 2.4 Hz, 1H), 6.84 (m,
3
2H), 6.66 (d, J(H,H) = 7.3 Hz, 1H), 6.44 (m, 1H aryl-H), 4.46 (d,
2
2J(H,H) = 12.5 Hz, 1H, CH2N), 3.83 (d, J(H,H) = 13.9 Hz, 1H, o-
C6H4CH2NMe2), 3.69 (d, 2J(H,H) = 12.5 Hz, 1H, CH2N), 3.25 (s, 4H,
free C6H5NCH2NMe2), 2.92 (d, 2J(H,H) = 13.9 Hz, 1H, o-
C6H4CH2NMe2), 2.23 (br s, 3H, o-C6H4CH2NMe2), 2.16 (br s, 3H,
NCH3), 2.05 (s, 12 H, free C6H5CH2NMe2), 1.58 (s, 9H, C(CH3)3),
1.40 (s, 9H, C(CH3)3), 0.98 (s, 3H, SiCH3). 13C{1H} NMR (100 MHz,
C6D6): δ 179.9 (d, 1J(C,Y) = 57 Hz, C−Y), 164.5 (CO), 161.0 (CO),
146.2, 141.7, 141.6, 140.0, 138.9, 138.4, 138.2, 137.6, 136.0, 135.7, 132.1,
131.9, 131.0, 129.6, 129.2, 129.1, 128.9, 127.2, 127.0, 126.6, 126.2, 125.6,
124.9, 124.7, 124.4, 123.7, 121.7, 120.3, 117.1 (aryl), 67.3 (CH2N), 64.5
(free C6H5CH2NMe2), 58.3 (CH2N), 45.4 (free C6H5CH2NMe2), 42.9
(N(CH3)2), 38.8 (NCH3), 35.4(C(CH3)3), 34.2 (C(CH3)3), 32.2
(C(CH3)3), 30.3 (C(CH3)3), −1.7 (SiCH3).
Determination of Enantiomeric Excess via Chiral HPLC. N-
benzoylation of Isolated Hydroamination Product. The hydro-
amination product (0.1 mmol) was dissolved in CH2Cl2 (1 mL), and
then DIPEA (26 mg, 0.2 mmol) and benzoyl chloride (21 mg, 0.15
mmol) were added. The mixture was stirred at room temperature for 3 h.
Volatiles were removed in vacuo, and the residue was partitioned
between Et2O (2 mL) and 2 M NaOH (2 mL). The resulting emulsion
was stirred for 2 h, and then the organic layer was separated, washed with
brine (1 mL), dried (Na2SO4), and concentrated. The residue was
purified by flash chromatography on silica (CH2Cl2), if necessary, or was
directly subjected to a chiral HPLC analysis. Absolute configurations of
intra-13d and intermolecular10b hydroamination products were assigned
1405
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Organometallics
Article
according to 19F NMR spectroscopic analysis of the corresponding
Mosher amides as described previously.
Chem. 2007, 2245. (g) Eisenberger, P.; Schafer, L. L. Pure Appl. Chem.
2010, 82, 1503.
N-(1-Methylhexyl)benzamide. Prepared from 17a. Colorless oil. 1H
NMR (400 MHz, CDCl3, 65 °C): δ 7.52−7.16 (m, 10H, aryl-H), 4.87
(5) Reviews on late-transition-metal-based catalysts: (a) Beller, M.;
Breindl, C.; Eichberger, M.; Hartung, C. G.; Seayad, J.; Thiel, O. R.;
Tillack, A.; Trauthwein, H. Synlett 2002, 1579. (b) Hartwig, J. F. Pure
Appl. Chem. 2004, 76, 507. (c) Widenhoefer, R. A.; Han, X. Eur. J. Org.
Chem. 2006, 4555. (d) Brunet, J. J.; Chu, N. C.; Rodriguez-Zubiri, M.
Eur. J. Inorg. Chem. 2007, 4711. (e) Hesp, K. D.; Stradiotto, M.
2
2
(d, J(H,H) = 15.2 Hz, 1H, CHN), 4.45 (d, J(H,H) = 15.2 Hz, 1H,
CHN), 3.94 (br s, 1H, CHN), 1.56 (br s, 1H), 1.31−1.05 (br s, 10H),
0.82 (m, 4H). A 13C NMR spectrum could not be acquired, as signals are
very broad and obscure due to rotamer interconversion. HPLC (AS-H,
hexane/2-propanol 90/10, 1 mL/min): tR 13.3 min (R isomer), 22.3
min (S isomer).
ChemCatChem 2010, 2, 1192. (f) Jenter, J.; Luhl, A.; Roesky, P. W.;
̈
Blechert, S. J. Organomet. Chem. 2010, 695, 406.
N-(1-Methyl-3-phenylpropyl)benzamide. Prepared from 17b.
Colorless oil. 1H NMR (400 MHz, CDCl3, 65 °C): δ 8.10 (d,
3J(H,H) = 7.8 Hz, 1H), 7.60−6.96 (m, 14H, aryl-H), 4.71 (br s, 1H,
CHN), 4.58 (d, 2J(H,H) = 14.5 Hz, 1H, CHN), 2.49 (br s, 2H), 1.99 (br
(6) Review on alkali-metal- and alkaline-earth-metal-catalyzed hydro-
aminations: (a) Seayad, J.; Tillack, A.; Hartung, C. G.; Beller, M. Adv.
Synth. Catal. 2002, 344, 795. (b) Harder, S. Chem. Rev. 2010, 110, 3852.
(c) Barrett, A. G. M.; Crimmin, M. R.; Hill, M. S.; Procopiou, P. A. Proc.
R. Soc. A 2010, 466, 927.
s, 1H), 1.17 (br s, 1H), 1.19 (d, 3J(H,H) = 12.3 Hz, 3H, CH3). A 13
C
NMR spectrum could not be acquired, as signals are very broad and
obscure due to rotamer interconversion. HPLC (AS-H, hexane/2-
propanol 90/10, 1 mL/min): tR 25.5 min (R isomer), 45.5 min (S
isomer).
(7) For selected examples of nonstereoselective intermolecular
hydroaminations of activated alkenes see: (a) Casalnuovo, A. L.;
Calabrese, J. C.; Milstein, D. J. Am. Chem. Soc. 1988, 110, 6738.
(b) Beller, M.; Breindl, C.; Riermeier, T. H.; Eichberger, M.;
Trauthwein, H. Angew. Chem., Int. Ed. 1998, 37, 3389. (c) Pawlas, J.;
Nakao, Y.; Kawatsura, M.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124,
3669. (d) Utsunomiya, M.; Kuwano, R.; Kawatsura, M.; Hartwig, J. F. J.
Am. Chem. Soc. 2003, 125, 5608. (e) Utsunomiya, M.; Hartwig, J. F. J.
Am. Chem. Soc. 2004, 126, 2702. (f) Johns, A. M.; Utsunomiya, M.;
Incarvito, C. D.; Hartwig, J. F. J. Am. Chem. Soc. 2006, 128, 1828.
(g) Horrillo-Martínez, P.; Hultzsch, K. C.; Gil, A.; Branchadell, V. Eur. J.
Org. Chem. 2007, 3311. (h) Yuen, H. F.; Marks, T. J. Organometallics
2009, 28, 2423. (i) Zhang, X.; Emge, T. J.; Hultzsch, K. C. Angew. Chem.,
Int. Ed. 2012, 51, 394. (j) Brinkmann, C.; Barrett, A. G. M.; Hill, M. S.;
Procopiou, P. A. J. Am. Chem. Soc. 2012, 134, 2193. (k) Liu, B.; Roisnel,
T.; Carpentier, J.-F.; Sarazin, Y. Angew. Chem., Int. Ed. 2012, 51, 4943.
(8) Selected examples of asymmetric intermolecular hydroamination
N-Benzoyl-2-methyl-4,4-diphenylpyrrolidine.33 Prepared from 11a.
1
Colorless oil. H NMR (500 MHz, CDCl3, 65 °C): δ 7.45−7.04 (m,
15H, aryl-H), 4.26−4.15 (m, 2H), 3.86 (br s, 1H), 2.93 (br s, 1H), 2.34
(m, 1H), 1.44 (br m, 3H). 13C{1H} NMR (125 MHz, CDCl3, 65 °C): δ
170.0 (CO), 145.6, 137.5, 128.6, 128.5, 128.4, 126.8, 126.63, 126.56
(aryl), 59.6, 52.7, 45.8, 30.7, 20.0 (CH3). HPLC (OD-H, hexane/2-
propanol 90/10, 1 mL/min): tR 13.0 min (S isomer), 21.9 min (R
isomer).
ASSOCIATED CONTENT
* Supporting Information
■
S
NMR spectra of ligand precursors, ligands, and complexes. This
material is available free of charge via the Internet at http://pubs.
acs.org.
involving activated alkenes: (a) Dorta, R.; Egli, P.; Zurcher, F.; Togni, A.
̈
J. Am. Chem. Soc. 1997, 119, 10857. (b) Kawatsura, M.; Hartwig, J. F. J.
Am. Chem. Soc. 2000, 122, 9546. (c) Lober, O.; Kawatsura, M.; Hartwig,
̈
AUTHOR INFORMATION
Corresponding Author
*E-mail: hultzsch@rci.rutgers.edu.
Notes
■
J. F. J. Am. Chem. Soc. 2001, 123, 4366. (d) Utsunomiya, M.; Hartwig, J.
F. J. Am. Chem. Soc. 2003, 125, 14286. (e) Hu, A.; Ogasawara, M.;
Sakamoto, T.; Okada, A.; Nakajima, K.; Takahashi, T.; Lin, W. Adv.
Synth. Catal. 2006, 348, 2051. (f) Zhou, J.; Hartwig, J. F. J. Am. Chem.
Soc. 2008, 130, 12220. (g) Pan, S.; Endo, K.; Shibata, T. Org. Lett. 2012,
14, 780. (h) Butler, K. L.; Tragni, M.; Widenhoefer, R. A. Angew. Chem.,
Int. Ed. 2012, 51, 5175. (i) Cooke, M. L.; Xu, K.; Breit, B. Angew. Chem.,
Int. Ed. 2012, 51, 10876.
(9) For nonstereoselective intermolecular hydroaminations of
unactivated alkenes see: (a) Li, Y.; Marks, T. J. Organometallics 1996,
15, 3770. (b) Ryu, J.-S.; Li, G. Y.; Marks, T. J. J. Am. Chem. Soc. 2003,
125, 12584. (c) Brunet, J.-J.; Chu, N. C.; Diallo, O. Organometallics
2005, 24, 3104. (d) Khedkar, V.; Tillack, A.; Benisch, C.; Melder, J.-P.;
Beller, M. J. Mol. Catal. A: Chem. 2005, 241, 175. (e) Baudequin, C.;
Brunet, J. J.; Rodriguez-Zubiri, M. Organometallics 2007, 26, 5264.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by the National Science Foundation
through an NSF CAREER Award (CHE 0956021).
■
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